问题
选择题
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
答案：D
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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：D