题目

男同学一般比女同学的声音沉闷、浑厚,这是因为男同学发声时（   ） A.频率高,振幅大   B.频率低,振幅小 C.频率低,振幅大   D.频率高,振幅小 答案：C.声音沉闷,是指音调低,故频率低.浑厚说明声音响度大,振幅大. Brian was about to_______________ when he suddenly found an answer to the question. 　　A. make up　　    B. look up　　       C. turn up　　       D. give up