◎ 题干
Computers are very useful in our lives, but they must        properly.
A. use                 B. be using                C. be used
◎ 答案
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◎ 解析
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◎ 知识点
    根据魔方格专家分析,试题“Computers are very useful in our lives, but they must properly.A. use B. be using C. be used…”主要考查了你对  【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。