Air pollution caused by industrial fumes has been studied for years, but only re

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试卷: SAT句子挑错练习01[查看]
Air pollution caused by industrial fumes has been studied for years, but only recently has the harmful effects of noise pollution become known.
A: has been studied
B: but
C: has
D: become
E: no error

参考答案: C

本题解释:
倒装语序，the harmful effects of noise pollution have become known