A Pragmatic Study on Teachers’ Feedback in EFL Classroom in China

EFL classroom teaching in China, no matter whether it is traditional one or a flipped one, is a dynamic communicative process by using English with the aim of learning it. The interactive discourse between the teacher and the student has its own pragmatic functions, especially the feedback given by the teachers which may influence the teaching and learning efficiency. In order to provide appropriate investigation resources, a corpus of 128,223 words with 36.65 hour-2199 minute real audiovisual college EFL classroom teaching transcripts is built. Taking the data of the resources as supporting evidence, this paper analyzes the pragmatic functions of EFL classroom feedback discourse, and proposes certain pragmatic strategies of increasing interactivity, which has certain pedagogical implications for EFL classroom teaching.


Introduction
In China, the EFL (English as a foreign language) classroom is the main place for English learning. The language input of learners mainly comes from the classroom, and the output mainly occurs in the classroom. The process of language interaction between teachers and students in the classroom is the process of English teaching and learning as a foreign language. Interactive adjustment of input to make it comprehensible and absorbed, creating opportunities to promote output, is the main and important part in foreign language teaching classroom, which determines the effectiveness of foreign language learning. How to make students accept as much comprehensible input as possible, how to create opportunities for students to participate in interaction and promote output are the challenges faced by College English teachers. English teachers should focus not on what we should teach, but on the conditions for promoting foreign language learning and how to create these conditions in the English language classroom. The process of foreign language classroom interaction takes place in the form of discourse. The research of EFL teaching in China has paid more and more attention to the study of EFL classroom discourse. The quality of classroom discourse, the choice of strategies, the mode of classroom interaction or negotiation, and feedback strategies will directly affect students' learning, cognition and language development. Therefore, the study of EFL classroom discourse is an important field in foreign language teaching, linguistics and second language acquisition. Now in China, EFL teaching is undergoing a pedagogical reforming and a renewal of teaching concept. Even though the development of science and technology has extended interaction to outside of the classroom, classroom teaching cannot be completely replaced. And there is no doubt that a flipped classroom is more interactive than a traditional one. The ultimate goal of language learning is to communicate. Interaction is the core of communication, and also a means of improving students' communicative competence. The discourse in classroom is different from that in natural communication; the discourse in EFL classroom also differs from that in the classroom using native language. It is of vital importance to analyze the dynamic process and interactive features of the interactive discourse in foreign language classroom, summarize the pragmatic principles in the interaction, and provide guidance for teachers and students to adopt appropriate pragmatic strategies under those principles so as to increase interactivity and achieve the ultimate goal of teaching and learning. The classroom feedback discourse is an important part of the classroom interactive discourse.

Literature Review
Conversation is a dynamic communicative process that occurs between two or more communicators. The speaker has to provide effective information related to the topic while the hearer must give verbal feedback to the speaker's speech, thereby demonstrating that he or she is engaging in dialogue. This principle, Cooperative Principle, is the basic pragmatic principle that conversation should follow. Both sides of communication have to be cooperative in the conversation before the conversation starts and proceeds. There can be various forms of feedback, such as gestures, eye contact, facial expressions, etc. to indicate his or her attitude towards the information provided by the speaker. In addition, hearers can also use speech in response, which is called feedback. Duncan (1973) points out that feedback, also known as "feedback discourse", is the response of the interlocutor to the current speaker's speech in the conversation.
Classroom discourse is a dynamic communicative process taking place between teachers and students, in which teachers and students are constantly changing their roles. That is teachers can be hearers and students can also be speakers. Acting as a speaker, the teacher usually asks hearers or students for information by asking questions. Based on the pragmatic rules of Cooperative Principle, students should respond to the teacher's questions. When a teacher turns into a hearer and listens to the students' speech, generally when answering the question, he or she should also make a feedback to demonstrate that he or she has been an active participant of the conversation. Class discourse is a process of cooperation between teachers and students, which cannot continue without the cooperation of either side.
Feedback is also a part of classroom interaction in second language acquisition. Selinger (1983) shows clearly that the aim of feedback is responding to the speech of the learner. In the process, the emphasis is the learner who is able to judge whether they understand the target language correctly. Gass & Selinker (2011) also point out that interactive feedback, the crucial source of information for learners, usually provides them with information if their discourse successfully continued and more opportunities to focus on language production or understanding.
Researchers have studied the different forms of influence of teachers' feedback on learners. Some studies have shown that the implicit negative feedback has correction function through negotiation (Gass & Varonis, 1989;Pica, Holliday, Lewis, & Morgenthaler, 1989). Nobuyoshi and Ellis (1993) found that native speakers sent different kinds of feedback to the errors of non-native speakers, and the most frequent modification was the response to clarification request, rather than seeking confirmation through demonstration. The results of Ellis, Loewen & Erlam (2006) show that in grammar acquisition, the effect of explicit feedback is significantly better than that of implicit feedback. And it has been found that more proficient learners prefer to get more elicitative kinds of feedback from the teacher, which may cause more self-correction (Shiva, Mohammad, & Sajjad, 2015;Milla & Mayo, 2014).
Generally speaking, teachers' verbal feedback in the classroom interaction can be divided into positive feedback and negative feedback (Larsen-Freeman, 2003). Long (1983) found that the most common method teachers utilize to correct students is restatement. Error correction has been a controversial type of feedback in SLA studies (Azad 2016;Kartchava & Gatbonton, 2020;McDonough & Sato, 2019). One group declares that too often correcting the errors made by students may break down their talk to pieces without favoring complete and coherent production, but another group testified that error correction can help English learning.
Chinese scholars have conducted feedback research in EFL learning environment. Li (2007) divided the feedback of teachers into positive feedback and negative feedback. Gu and Wang (2009) discuss the concept and nature of recasting and expound its corrective nature dialectically. At the same time, they analyze the role recasting plays in second language acquisition and factors influencing the role. Gong (2004) also studies deeply the relationship between the form of teachers' feedback and the degree of students' anxiety in the classroom and proposes that teachers should establish a good relationship with students in order to lower students' anxiety level and turn "input" into "absorption" effectively. Zhuang (2012) analyzes corrective feedback of teachers and response and assimilation of students in English classrooms, finding out that induced feedback can provoke absorptive responses most effectively. Wei (2015) applies the experimental method to explore the effects of recasting and prompting on the learner's pragmatic acquisition and finds that classroom feedback has a positive effect on pragmatic acquisition, the effect of promoting request the most obvious. J. Xu, Fan & Q. Xu (2019) investigates EFL learners' corrective feedback decision-making in task-based peer interaction. Their study found in EFL learning environment learners favored recast over prompts and explicit correction in responding to their peers' linguistic errors.
In conclusion, studies on classroom feedback are abundant mostly from the perspective of SLA and education. Researchers' focus is on the role of certain kind of feedback in helping English learning, but it's rare to find the studies of feedback discourse from the pragmatic angle. What pragmatics studies is the discourse happening in a certain language environment, which in this study is teachers' feedback discourse in EFL classroom. Verschueren (1999) thought pragmatic study is from a functional perspective on (any aspect of) language. This study aims at finding the pragmatic functions of EFL classroom feedback discourse, proposing pragmatic strategies of increasing interactivity in the EFL classroom, which may have certain pedagogical implications for EFL classroom teaching.

Research Questions
The research mainly answers questions as follows: 1) What are the pragmatic functions of various feedback discourses in the EFL classroom?
2) What are the most common types of feedback discourses in the EFL classroom?
3) What type of feedback discourse is more conducive to the understanding and language production for foreign language learners? 4) What feedback pragmatic strategies should teachers use to promote the interactivity of the EFL classroom?

Research Methods and Tools
In this research, the method of self-built corpus and conversation analysis are utilized to transfer the 36.65 hour-2199 minute real audiovisual corpus in classroom from 12 English teachers to build a mini-corpus of 128,223 words. The transliteration adopts the transliteration system (Atkinson & Heritage, 1984) commonly used by the American school of conversational analysis (as cited in H. Liu, 2006), all of which are transferred into text and proofread artificially. Twelve teachers are from seven key universities in five regions of Guangdong, Shanghai, Beijing, Sichuan and Hunan. The courses, as English language skill courses involve five types of courses: listening, speaking, reading, writing, and translation, of which six are national quality English major courses, one excellent demonstration course at school level. The names of the regions and courses referred to in the corpus are shown in Table 1.

Findings
This research uses the category of Larsen-Freeman (2003) to divide feedback discourses of teachers into positive feedback and negative feedback. Based on corpora analysis and pragmatic functions of various feedback discourses, positive feedback discourses are classified into general supportive feedback, repetition, evaluation, assistance acknowledgement, explanation, continuing to ask questions, and making requests, while negative elt.ccsenet.org Vol. 14, No. 5; feedback discourses are divided into explicit correction, request for clarification, and restatement. See details in Table 2. Among the positive feedback category, the first type is general supportive feedback discourses. General supportive feedback indicates merely that the hearer is listening to the speaker's speech or expresses a low degree of consent.
According to previous researches, although general supportive feedback discourse in the classroom accounts for a small proportion of all positive feedback, it promotes the interaction between teachers and students to a large extent. General supportive feedback usually uses interjections, such as "Yeah", "Um", "Uh-huh", which have no exact meanings but implicit pragmatic meanings, demonstrating teachers' approval, satisfaction, or doubt. Here is an example: (1)L5: I think it is hard to say it is rude or so but it's um based on their culture

ok ok(+) yes yes(+) ok good good(+) so certainly here it is inappropriate…
In example (1), there are eight positive feedback utterances, six of which are general supportive feedback: "uh-huh", "um", and "ok". These words have no meaning per se, but when hearing them, the student goes on speaking without the teacher asking further questions. It proves that general supportive feedback discourse can not only express participation, acceptance, and recognition, but also implies that the conversational turn has yet to be finished, thus encouraging the student to continue speaking, until he hears evaluative feedback from the teacher and decides that his turn is over. As is shown in the example, the student's turn is over when the teacher gives highly favourable feedback "Ok, ok, yes, yes, ok, good, good", indicating that the teacher is going to comment upon the student's answer. But not in all situations can general supportive feedback serve this purpose. It generally depends on the relationship between the teacher and the student: When the student is not worried about being criticized or losing face, he is more likely to take an active part in the interaction and have more language output. Also, it has something to do with the student's language proficiency and communicative ability. If the student, with a weak pragmatic awareness, is not aware of the pragmatic meaning of this form of feedback, he will not go on speaking.
Type 2: repetition The second type of positive feedback is repetition. Repetition exists naturally in language use. Seen and heard everywhere in people's daily use of language, it is one of the important means of verbal communication.
Repetition plays a vital role in language use: It is one of the important ways to make the conversation go smoothly and clarify the content of communication, and it is also an indispensable part in studies on cooperative principle, a form of adhering to the politeness principle, and one of the important processes changing "input" into "absorption" in second language acquisition. From a pragmatic point of view, repetition serves the purpose of politeness, clarification, cooperation, confirmation, and restart. From the perspective of language learning, repetition can strengthen memory. From the perspective of teaching, repetition is used for emphasis. Repeating students' words expresses affirmation, and sometimes also implies that the students need to correct the errors in those words.
As a form of positive feedback, repetition occurs frequently in classroom teaching. According to the corpus analysis, the pragmatic role of repetition in the interaction between teachers and students can generally be divided into six types: accepting, emphasizing, implying the need for correction, continuing the topic, requesting clarification, and enlightening further. Here is an example: (2)L9: the cloud is beautiful as the silk of a small fairy The teacher first repeats the student's one word: "as", a word which is part of a phrase. The teacher's repetition of this single word is intended to remind the student of the error in his utterances. The student realizes the pragmatic meaning of the feedback and corrects the language form. Finally the teacher repeats the corrected words, showing approval. Here is another example: ( 3) The teacher gives repetition feedback, without adding evaluative feedback or asking further questions, and the student goes on speaking on his own. But not all repetition feedback can trigger further output from the student like this. It depends on the distance of relationship between the teacher and the student and the pragmatic ability of the student.
Repetition is a linguistic phenomenon with complex functions, and an important topic in the study on classroom discourse. Teachers should consciously use repetition for feedback in teaching, but should not overuse it. Proper repetition can attract students' attention and provoke thought. Excessive use of it, however, will disorganize the classroom teaching and weaken the teaching effect. Either too much or too little of repetition violates pragmatic rules and the politeness principle and leads to a failure to achieve the intended purpose of communication.
Type 3: evaluation The third is evaluation. Evaluation is a kind of positive feedback showing high degree of support. It appears frequently in foreign language classrooms. It is a praise given by teachers to students. Analysis of the corpus concerning 12 teachers shows that appreciative evaluation usually occurs in the following three situations. First, when the student has finished speaking, the teacher gives appreciative feedback on the content, views and language form of the student's answer. Secondly, when the student's answer is incomplete, the teacher gives appreciative feedback, after which some students will go on speaking, and sometimes the teacher continues to ask questions. Thirdly, when the teacher does not understand the student's answer, he gives appreciative feedback before asking for clarification. Here is an example: In example (4), the teacher does not fully agree with the student's answer, as can be seen from "but there's room for improvement". But the teacher gives appreciative positive feedback "very good" rather than negative feedback. The teacher's feedback saves the positive face of the student. It is conducive to the interpersonal communication between the teacher and the student, and helps to trigger more interaction. Learners all hope to get approval or praise from teachers. When giving feedback, teachers should consider how to save the positive face of learners and stimulate their interest and motivation, while at the same time pointing out their errors, thus achieving the best feedback effect.
Type 4: offering help The fourth kind of positive feedback is offering help. When students can not continue speaking because of difficulties of language form or content, most teachers will give positive feedback of offering help. According to the corpus analysis, there are three forms of such feedback: helping directly, completing the discourse, and helping indirectly. Here is an example: In example (5), the student met with difficulty in expressing ideas and fails to complete the discourse. After a few seconds of pause, the teacher realizes the student's difficulty and helps to complete the discourse. After the feedback of offering help, the teacher continues to use the pragmatic strategy of unfinished discourse to help the student finish his conversational turn. Letting the student complete the discourse not only saves the positive face of the student, but also fulfills an interaction of meaning-negotiation concerning a topic.

Type 5: acknowledgement
The fifth is acknowledgement. Acknowledgement means that in verbal communication, the listener expresses thanks for the positive comment given by the speaker. By expressing thanks, the feedbacker shows active cooperation with the current speaker, and also complies with the politeness principle. In the classroom, acknowledgement feedback usually occurs when the student gives the right answer, and the teacher expresses thanks for the cooperation of the student answering the teacher's question.

L4: (+) ugh-we will, ugh,(+) think about naturally about the person(+)(+)who leave us. and-we will remember the memory-we share with(+) T: Ok, Ok, thank you, thank you. (+)(+) Basically I don't think you have that much experience of, you know, saying goodbye to someone on the funeral.
In the example, the student's responses exceeded the teachers' expectations. The teacher gave a high degree of thank you feedback, repeated the feedback "thank you" twice, expressed her gratitude for the cooperative speech act of the student, and ended the students' turn. After most of the acknowledgement feedback, the student stops talking, and the teacher continues speaking or starts new discourse. So acknowledgement is usually the signal of the end of a conversation. However, for the appreciative feedback given by teachers, almost no student gives acknowledgement feedback. In verbal communication, according to the communicative and pragmatic principles, when the current speaker receives appreciative feedback, he should thank the feedbacker for the praise. There exists no such interactive mode in the corpus. It proves that the communicative context in the classroom is different from that in natural communication, and the classroom discourse has specific pragmatic features. It also proves in another way that the students' pragmatic awareness is not strong enough to practice pragmatic principles in natural conversation.
Type 6: explanation The sixth kind of positive feedback is explanation. Teachers use explanatory feedback to supplement and explain students' answers, clarify language points, express their opinion, or introduce new knowledge. Most explanatory feedback can be followed by asking further questions, clarification or other types of positive feedback, for example:

(7)T: No(+)OK(+)the first two words(+)hiking(+)swimming(+)but the third one changed into infinitive(+)so the third word should change into L: riding T: riding(+)yeah(+)riding a bicycle(+)you can just use(+)bicycling(+)Mary likes. hiking(+)swimming(+)and bicycling(+)so we parallel(+)parallel structure here…
In the example, the teacher explained and fed back the language form of the word "riding" and gave the correct language form after the correction, without giving the negative feedback directly to the form error of the word, which saved the face of the student and made the student more receptive to the correction emotionally.

Type 7: asking further questions
The seventh is asking further questions. This mode appears frequently in the classroom. In this mode, the teacher asks questions first, then after the student's response, the teacher's feedback is to ask further questions and let the student respond again. After several rounds, the teacher gives the final feedback. The reasons why the teacher asks further questions may be that the student's answer is inaccurate or incorrect, and the teacher wants the student to correct by himself or may also be that the teacher raises questions about different aspects of a topic, and finally presents the whole picture by rounds of Q&A. Asking further questions hands the conversational turn back to the student, who has to answer again, thus having more opportunities to interact and output language, for example:

T:Yes(+) catastrophic accidents(+) now you see(+)such as the car crush(+)OK(+)and(+)yes firs(+)and what about that one?(+)yes(+)explosions
Type 8: making requests The eighth is making requests. Making a request means asking firmly, and not expecting to be rejected. In daily conversations, it is impolite to make requests. However, because teachers have greater power in the classroom, they can make some requests concerning language learning for students. But this kind of situation seldom elt.ccsenet.org English Language Teaching Vol. 14, No. 5; happens, because it violates the pragmatic principle, affects the communicator's emotion, causes the communication to be frustrated.

Negative Feedback
Negative feedback, also called corrective feedback, refers to the evaluative and guiding information given by teachers targeted at learners' language errors (Larsen-Freeman, 2003: 28). In foreign language classrooms, teachers are also foreign language learners. How to respond to students' errors and how to organize language is very worthy of study. Analysis of the transcripts shows that teachers' corrective feedback in foreign language classrooms mainly includes direct correction, asking for clarification, and recasting.
Type 1: direct correction The first type of negative feedback is direct correction. It means that when the teacher identifies errors in the student's expression, he directly points out the errors, and rectifies them himself or asks the student to do it. The errors are usually in four aspects: pronunciation, grammar, diction and understanding, for example:  (9), as for the pronunciation of the word "moan", the teacher corrected the student's phonetic errors clearly, and directly gave the correct demonstration. The student imitated the teacher's pronunciation and made feedback response. In example (10), the correction feedback is aimed at different grammatical meanings of "amazing" and "amazed". When the teacher heard the error, he directly interrupted the student's speech, corrected it, and gave the explanation feedback.
Type 2: asking for clarification The second type is asking for clarification. Teachers often ask students to explain or repeat their answers when teachers do not agree with, do not hear clearly, or have doubt about the answers. Such feedback and questioning for clarification share the same pragmatic function. They both appear in the feedback move. Questioning for clarification is a form of feedback asking for clarification. Apart from asking questions, teachers can also say "sorry?" or "pardon?" with a rising intonation, or repeat the student's answer with a rising intonation, or asks "Are you sure?" or others to prompt the student to correct the answer, for example: (11) L1: um(+) and also people um some little um some small childrens um(+) fire the bonfire and firecrackers //um// T: //are// you sure? Are we allowed to do that? Firecrackers?

L1: yeah firecrackers T: yes? Ok good (hhh) anything else?
Type 3: recasting The third is recasting. Lyster and Ranta (1997) defined recasting as repeating all or part of the content of the students' utterances except errors therein. The purpose of the recasting feedback is to rectify learners' language errors so as to promote understanding and make the communication clear and accurate. In actual teaching, teachers should follow the principle that recasting should not interrupt the harmony and fluency of communication. If learners are interrupted by teachers' recasting feedback when they are stating their points of view, the fluency of the communication can be ruined, and the effect of feedback may not be as good as that of letting the communication flow on.
There are mainly two forms of recasting that are found during analysis of the transcribed teaching videos: recasting of linguistic forms and recasting of meaning. The former refers to the recasting of students' errors in pronunciation, vocabulary, grammar, etc. The latter is not targeted at those formal aspects, but rather restates, in reorganized language, the meaning extracted from students' utterances. Here is an example of meaning recasting: T: So we say she is quite a traditional Chinese mother. Since you mentioned word like straight, like very traditional Chinese mother.
In example (12), when answering the teacher's referential question, the student expresses his meaning clearly. But although he makes no error in pronunciation, vocabulary or grammar, the sentence pattern is uneconomical, and the language form is not accurate enough. The teacher gives recasting feedback, letting the student realize his shortcomings, as well as setting a good example. In example (13) there are many errors in language form in student's answers to teacher's reference question, and the expression of meaning is not clear enough. The teacher does not repeat for individual errors in language form, but reorganize the expression of language form after understanding student's meaning. Wen and K. Li (2009) said, "The recasting feedback is one of the important sources of comprehensible input for foreign language learners. Whether or not it can promote communication still depends on how well the teachers use feedback strategies. Successful recasting feedback can increase the students' language output, thus enhancing the learning and teaching efficiency." (p. 87) Therefore, the research on recasting is of great significance to the study on and practice of foreign language learning in China. Teachers should adopt a variety of recasting feedback modes according to the specific teaching environment and the actual situation of the students, adopt effective interpersonal pragmatic strategies, and commit themselves emotionally to teaching and try to elicit positive emotional changes in students, altogether increasing interactivity and improving teaching and learning efficiency.

Statistical Analysis
The frequency of the teachers using each type of feedback and its share of all feedback are shown in table 3, figures 1 and 2:  T1 T2 T3 T4  T5  T6 T7  T8 T9 T10 T11  1) The amount of positive feedback (916 times) is more than that of negative feedback (102 times), accounting for 90% and 10% of all feedback respectively. The teachers are more inclined to give positive feedback on the students' answers. Even if the students make errors, the teachers tend to use positive feedback such as repetition or explanation to attract attention and help to correct the errors.
2) General supportive feedback discourse appears most frequently, accounting for 27.6% of all feedback. It usually only indicates that the listener is listening to the speaker, or shows a low degree of agreement. Previous studies show that general supportive feedback accounts for a very small proportion of all positive feedback, but this is not the case according to the results of the corpus analysis. General supportive feedback can greatly facilitate the interaction between teachers and students. It is capable of not only expressing participation, acceptance, and recognition, but also implying that the conversational turn has yet to be finished, thus encouraging the student to continue speaking.
3) Repetition, making up 20.7% of the total, is the most common form of feedback after general supportive feedback. Repetition has the pragmatic functions of coordination, cooperation, politeness, clarification, confirmation, testing, and restarting. As a type of teachers' feedback discourse in foreign language classrooms, it specifically serves the purpose of accepting, emphasizing, implying the need for correction, continuing the topic, requesting clarification, and enlightening further. 4) Asking further questions accounts for 17% and is also one of the most common feedback methods. The teachers delay the feedback and continue to ask questions. This is the most direct way to trigger more interaction and increase the language output of the students. 5) Explanation makes up 8.4% of all feedback. Explanatory feedback supplements or explains the students' answers, clarifies language points, conveys the teachers' ideas or introduces new knowledge. It is an important source of the students' language input. 6) Recasting, accounting for 6% of the total, does not have the highest percentage of all feedback as Lyster and Ranta (1997) found out, although it is most common in negative feedback.
7) The least used methods are making requests, which belongs to positive feedback and occupies 1.5%, and asking for clarification, which belongs to negative feedback and occupies 1.4%. 8) These feedback methods are not used by the teachers individually. Even one feedback move often contains a combination of several methods, and their appearance presents certain patterns, for example, general supportive feedback ---repetition--asking further questions, general supportive feedback ---evaluation --asking further questions, repetition ---evaluation ---asking further questions, etc.

Conclusion and Enlightenment
Teachers' positive feedback in foreign language classrooms is different from positive feedback in other fields. It has its own features. According to the statistical analysis, general supportive feedback, repetition and asking further questions are the most common feedback methods used by teachers. The first two have multiple pragmatic meanings. They are used by teachers to indirectly express acceptance, praise, and emphasis, and trigger more interaction with students. These methods do not threaten students' right to speak, and can maintain the interaction between teachers and students. Asking further questions is the most effective way for teachers to keep the students in the interaction. Teachers' dominance in the classroom enables them to request students to go on speaking or answering questions. But this must be done in a way that avoids teachers' role becoming the role of examiners. Classroom verbal interaction is still a kind of interpersonal interaction. Although there is a power gap between teachers and students as participants, teachers should adopt appropriate pragmatic strategies to narrow the gap and try to sustain the interaction.
Evaluation, acknowledgement, and explanation have the pragmatic meaning of taking the conversational turn from the students. In order to elicit more rounds of interactive discourse and provide more chances of output for students, teachers should delay the use of these methods.
There is more positive feedback than negative feedback in the corpus, accounting for 90% and 10% respectively. This indicates that teachers rarely correct students' errors. Whether or not to correct students' errors and when and how to do it has long been a controversial topic. Krashen (1982) proposed that rectifying learners' mistakes will affect their emotions and render them self-protective, which is not helpful in language acquisition. But some other researchers believed that learners' errors must be corrected in time. Schmidt and Frota (1986) said, "Any one learner's language output is also the input of the whole class. If the teacher does not correct the speaker's errors in time, this student and the other students may mistake the errors for correct expressions, and internalize those errors" (as cited in X. Zhou & Y. Zhou, 2002, P. 64). Whether or not to correct errors still needs in-depth study considering China's specific foreign language teaching context.
Negative feedback corrects errors in students' utterances. It involves not only the corrective information, but also the forms through which the information is conveyed. It should be an integration of content and form, combining expressiveness and decency. According to the "face theory" proposed by Brown and Levinson (1987), all of the teachers' speech acts in negative feedback are essentially "face-threatening acts". Learners all want to be approved of and praised by teachers, so when giving negative feedback, teachers should consider how to save the positive face of learners and activate their motivation, while at the same time pointing out their errors, thus achieving the best feedback effect. Compared with direct correction and asking for clarification, recasting feedback can effectively integrate content and form, serving both purposes of correcting errors and maintaining the positive face of the students. The actual statistics also show that, recasting is the most commonly used negative feedback.
Teachers' feedback discourse is uttered in the classroom discourse context, and is part of the classroom communicative acts. The classroom discourse context is dynamic. It is constantly being reconstructed in the interaction between teachers and students. A dynamic chain of "trigger ---response---feedback" is formed as the basic mode of the classroom discourse. Teachers should give feedback on students' speech acts according to the changing context. The corpus analysis shows that positive feedback appears frequently in foreign language classrooms. Among the eight types, general supportive feedback (S), evaluation (E), repetition (R), and asking further questions (Q) are often combined to be used. Facts prove that these four methods can trigger more interaction and language output, so they should be recognized and promoted in actual classroom teaching. The way they are combined is not fixed. Different combinations will appear as the dynamic context changes, as is shown in figure 3:

Figure 3. Modes of Teachers' Positive Feedback Discourse in EFL Classrooms
From the above discussion, it can be seen that teachers' feedback is closely connected with the classroom interaction. It can greatly promote students' understanding, increase interactivity and trigger more output. Teachers' feedback is a vital part in the interaction chain. It provides students with opportunities and motivation to output language. Most foreign language teachers in China are only advanced foreign language learners, and they can not quite use the language skillfully to give feedback. It is very important for teachers to know how to give feedback and which feedback methods and pragmatic strategies to adopt, so as to maximize students' input, increase interactivity and output, and optimize the classroom interactive process.