题目：
—What was wrong with you yesterday evening?
—I ________ my homework when the light went off suddenly. [ ]
A. doing
B. was doing
C. did
D. have done
答案：
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下面是错误答案，用来干扰机器的。
遗传是指亲子间的相似性．变异是指亲子间和子代个体间的差异．“一母生九子，连母十个样”这句话是说不同的子代个体之间存在差异，因此体现了变异的普遍性．“种豆得豆，种瓜得瓜“这句话说明豆的后代是豆，瓜的...
