Recently, the serious problem of smog caused by PM2.5______greatly by the govern

游客2023-09-20  34

问题 Recently, the serious problem of smog caused by PM2.5______greatly by the government’s effective measures.

选项 A、improved
B、had improved
C、has been improved
D、has improved

答案 C

解析 本题考查句子时态。句首的Recently一词提示,本题应使用现在完成时态;分析句子成分可知,主语是the seriousproblem,主语和谓语动词improve存在被动关系,故空格处所填动词应为第三人称单数形式,且使用被动语态。所以,C)为本题的正确答案。
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