◎ 题干
By the time he realizes he ______ into a trap, it'll be too late for him to do anything about it.
[      ]
A. walks
B. walked    
C. has walked      
D. had walked
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“By the time he realizes he ______ into a trap, it'll be too late for him to do anything about it. [ ]A. walks B. walkedC. has walkedD. had walked…”主要考查了你对  【现在完成时】  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。