[单选题]

胎膜自然破裂大部分发生在

A.临产后宫口开大6~7cm

B.临产后宫口开大4~5cm

C.临产后宫口开大2~3cm

D.临产后宫口近开全

E.临产后宫口开全后

参考答案与解析: