引起产后出血常见的胎盘因素不包括（）
A.胎盘滞留
B.胎盘钙化
C.胎盘粘连
D.胎盘残留
E.胎盘植入
参考答案：B
若3x=12，3y=4，则3x-y=______．
Who would you rather____the speech instead of you?
A．deliver
B．have delivered
C．have deliver
D．have to deliver
