◎ 题干
You should understand the traffic rule by now. You've had it _____ often enough.

[     ]

A. explaining
B. to explain
C. explain
D. explained
◎ 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“You should understand the traffic rule by now. You've had it _____ often enough. [ ]A. explaining B. to explain C. explain D. explained …”主要考查了你对  【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。