◎ 题干

7.Although the causes of cancer ____, we do not yet have any practical way to prevent it.  
A.are being uncoveredB.have been uncovering
C.are uncoveringD.have uncovered
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“7.Although the causes of cancer ____, we do not yet have any practical way to prevent it. A.are being uncoveredB.have been uncovering C.are uncoveringD.have u…”主要考查了你对  【现在进行时】【现在进行时的被动语态】  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。