◎ 题干
I _____ my homework when the door bell _____.  
[     ]
A. did; rang  
B. was doing; was ringing    
C. did; was ring    
D. was doing; rang
◎ 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_____ my homework when the door bell _____. [ ]A. did; rang B. was doing; was ringingC. did; was ringD. was doing; rang…”主要考查了你对  【实义动词的过去式】【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。