GB6675-2003规定：硬质弹射物的端部的半径应不小于（）mm。
A.2
B.3
C.4
D.5
参考答案：A
I believe it’s for the reason___ he had to drop out of school and left his hometown.
A．why
B．how
C．what
D．that
导致慢性胎儿窘迫的原因是（）
A.脐带绕颈
B.胎盘早剥
C.孕妇低血糖
D.胎盘功能不全
E.宫缩过强或持续时间过长
