单选题The little child usually&

单选题 The little child usually felt frightened at night, so not until ___________.A.did he fall asleep his mother left the roomB.he fell asleep had his mother left the roomC.did he fall asleep did his mother leave the roomD.he fell asleep did his mother leave the room

D解析考查倒装句，not until 放在句首时，从句不倒装，主句倒装，可排除A和C两项，B选项从句没倒装，主句倒装了，但是主语后的动词应用原形，所以不正确。故选D。

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