问题补充:
16. There was so much noise produced by the machine outside that the professor had to his voice so that it would not .
A. rise; be drowned
B. lift; drown
C. increase; drown
D. raise; be drowned
答案:
A. rise; be drowned
B. lift; drown
C. increase; drown
(答案→)D. raise; be drowned
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