求各位大神帮忙做道选择题

如题。
关于压缩模式下面哪种描述是正确的
A It will reduce the interference for other users
B It is not supported by some phones
C It will ruduce the speech quality
D It will result in an increased transmitted power

选择正确答案并说下理由，谢谢了

A吧？我是用的排除法。

同意选C，理由同楼上！