◎ 题干
A study ________ in the U.S.A. in 1977 showed that the chemical ASA in aspirin could prevent a stroke.
A. carrying out    B. carried out    C. working out    D. worked out
◎ 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“A study ________ in the U.S.A. in 1977 showed that the chemical ASA in aspirin could prevent a stroke. A. carrying out B. carried out C. working outD. wo…”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。