Thus to give a long instruction, the teacher can make it into different parts by using some pauses in the sentences。 What is more, the teacher can also use words like ‘yeah’, ‘ok’, ‘right’, ‘well’, and ‘hmm/em/er’instead of silent pauses to slow down the speed in order that student can have a better understanding。

B。  Rate of speech

It has been indicated that compared with some other language contexts, the teachers' speech in the second language class is much slower (Chaudron, 1988)。 Except for pauses, there are many experimental studies (see Henzl 1979, Hakansson1986, quoting from Giffiths, 1990) on the temporal variables have indicated that the slower speech rate could often make a difference to listeners。 A study of Swedish teachers' classroom talk held by Hakansson in 1986 showed that teachers used to make an adjustment of their speech rate to adapt the listeners' requirements (ibid。)。

So, in the foreign language class, it may be helpful to students’ understanding of TT by slowing down the speech rate or stressing important words so that they can pay attention to the crucial information。

2。3。2 The effect of lexis on listening comprehension

As for the lexical strategy, many studies (Henzl, 1979, Ke1ch, 1980, quoting from Chaudron 1988) have found that the teacher tends to choose some basic vocabulary items so that students can have a better comprehension of TT。 Henzl proposed that the words selected were stylistically neutral (e。g。 less colloquial一‘man’ instead of `young boy') and more concrete and proper nouns in included (e。g。 ‘Mrs。 White’ instead of ‘a kind woman’), and indefinite pronouns is seldom used。 

Basic vocabulary could not only help students understand the TT better and more easily, but also could help them master the second language more quickly。 Cook (1982) indicated that according to prototype theory, what second language learners first got were basic words, like ‘table’，then more general words like ‘furniture’, and finally more specific words like ‘coffee table’。 He claimed: ‘the basic level vocabulary is easier to use and to learn。’ Therefore the use of basic words can make it easier to understand TT。

2。3。3 The effect of syntax on listening comprehension

It has been found that some strategies of syntax can help the students' listening comprehension of TT。 Cervantes (1992) has indicated that linguistic simplifications, including syntactic simplification ‘clearly help make input language more comprehensible。’ His experiment on the syntactic simplification and repetition indicated that a syntactically simplified speech may help students understand better than a complex one。

Syntactical simplification might be realized by sampling sentence structure, sentence type and sentence length。 Tsui(1995:55) thought that teachers have the tendency to use better-formed, shorter sentences, fewer subordinate and conditional clauses。 In the English language, it is known that the complex sentence combines more subordinate clauses than other types of sentences。 Therefore, in spoken English, less complicated sentences could help people understand better。 

2。3。4 The effect of Modification devices on listening comprehension

    Many modification devices can be used to help listeners have a better comprehension of speaker’s meaning。 Tsui (1995) indicated that there are six modification devices in which clarification request confirmation check and repetition request are used by teachers to understand the students' input while comprehension check, self-repetition and decomposition are devices used to make them have a better understanding。 So, these three modification devices will be used in CI in order to make their meaning comprehensible。