◎ 题干
I saw your enjoyable magazine while _____ my homework.
[     ]
A. I did  
B. I am doing
C. I was doing  
D. I do
◎ 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“I saw your enjoyable magazine while _____ my homework.[ ]A. I didB. I am doingC. I was doingD. I do…”主要考查了你对  【过去进行时】  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。