◎ 题干
During the flood many students volunteered ________ through the weekend, giving out food and water for the victims.
A.workingB.to work
C.to have workedD.having worked
◎ 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“ During the flood many students volunteered ________ through the weekend, giving out food and water for the victims.A.workingB.to workC.to have workedD.having w…”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。