羊水栓塞常发生在下列哪些情况
A.胎盘早剥
B.剖宫产
C.子宫破裂
D.前置胎盘
E.二卵双胎
参考答案:A, B, C, D
—I had the computers repaired yesterday.
—How much did they _________ for that?
A.cost
B.spend
C.take
D.charge
数据库系统中实现各种数据管理功能的核心软件称为 【4】 。