问题
单项选择题
Since we can't hear you at the back of the hall, you'll have to（）your voice.
A.improve
B.increase
C.raise
D.open
答案
参考答案：C
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Since we can't hear you at the back of the hall, you'll have to（）your voice.
A.improve
B.increase
C.raise
D.open
参考答案：C