◎ 题干
For some time the expert __________ people of the health risks caused by passive smoking. He     says he won't stop until all the smokers around him decide to quit smoking.
A.is warnedB.is warningC.has been warningD.has been warned
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“For some time the expert __________ people of the health risks caused by passive smoking. He says he won't stop until all the smokers around him decide to quit…”主要考查了你对  【一般现在时】【将来进行时】【过去完成进行时】【过去将来时的被动语态】  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。