Unitl tens of years ago, most zoos      in such a way—animals in one area and birds in another.

A．were organized

B．had organized

C．will organize

D．have been organized

该患者最大可能为

A．完全性前置胎盘

B．部分性前置胎盘

C．边缘性前置胎盘

D．胎盘早剥

E．早产