People used to believe the earth was flat, ______?
A、
usedn't it
B、
wasn't it
C、
don't they
D、
didn't they
【正确答案】
D
【答案解析】
本题考查used to的反意疑问句。词组used to的反意疑问句有两种：一是didn't+主语：二是usedn't+主语，故选D。
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