题目内容
— When did the bell ring for the fire alarm?
— At 9 a.m. this morning, when we _________ morning exercises in the playground.
A.do B.are doing C.did D.were doing
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题目内容
— When did the bell ring for the fire alarm?
— At 9 a.m. this morning, when we _________ morning exercises in the playground.
A.do B.are doing C.did D.were doing