在教学过程中，以下什么行为将会降低教员的威信，同时也影响学员对教学内容的理解？ In the teaching process, which of the following will reduce instructor's prestige, but also affects the students understand the content of teaching?
A.采用过于抽象教学的教学方法 The teaching methods are too abstract
B.使用生动活泼的语言 Used lively and vivid language
C.语法错误及用语粗俗 Grammar mistakes and coarse language
正确答案是C