◎ 题干
--- He looks so tired. What’s wrong?
--- Nothing serious. He just stayed up last night, ___________his papers.
A.to prepareB.having preparedC.preparedD.preparing
◎ 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“--- He looks so tired. What’s wrong? --- Nothing serious. He just stayed up last night, ___________his papers.A.to prepareB.having preparedC.preparedD.prepa…”主要考查了你对  【现在分词的被动式】【现在分词】【不定式的被动式】【过去分词】  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。