求翻译：近20年来，对教师语言的研究主要集中在教师语言的使用和表达效果方面。因为教师能否恰当地使用教学语言，以及能否取得良好的语言表达效果，将会影响到课堂教学的效果，影响学生学习的效率。是什么意思？

The past 20 years, the study of language teachers, teachers focused on language use and effect of the expression. Because the ability of teachers to use appropriate language of instruction, and language ability to obtain good results, will affect the effectiveness of classroom teaching, impact on st

In nearly 20 years, the study focused mainly on teachers' language teachers in the use of language and expression in effect. Because teachers can appropriately use of teaching language, as well as the availability of good results, it will have an effect on language teaching and learning in the class

In the recent 20 years, mainly concentrate to the teacher language research in the teacher language use and express the effect aspect.Whether because the teacher does use the teaching language appropriately, as well as whether obtains the good language expression effect, will be able to affect the c

Nearly 20 years, the research of teacher's language is mainly concentrated in the terms of use and expression effect of teacher's language. Because teachers can properly using the language of instruction, as well as the availability of good language expression effect, that would affect the classroom

The past 20 years, the study of language teachers, teachers focused on language use and effect of the expression. Because the ability of teachers to use appropriate language of instruction, and language ability to obtain good results, will affect the effectiveness of classroom teaching, impact on st