◎ 题干
We must do something to _____ the factories sending out   poisonous gases so as to keep the
city_____.      
[     ]
A. keep; being polluted      
B. keep; from being polluted    
C. prevent; being polluted      
D. prevent; from being polluted
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“We must do something to _____ the factories sending outpoisonous gases so as to keep the city_____.[ ] A. keep; being pollutedB. keep; from being polluted C…”主要考查了你对  【动词短语】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。