导致滑胎的机理有二：其______；其二______。
参考答案：母体冲任损伤 胎元不健
Look at the picture.
A. It's nice.
B. Near the door.
电转机拔出主销，移动动作杆，顶杆上升行程不小于（）mm。
A.2.0
B.2.2
C.1.5
D.2.5
