胎儿出生后心血管系统的变化不包括（）

A.脐动脉和脐静脉闭锁

B.动脉导管闭锁

C.左、右心房完全分开

D.卵圆孔闭锁形成卵圆窝

E.膀胱圆韧带和肝圆韧带断开

It is necessary to secure the forced ventilation to a compartment where there is a fire to（）.

A.allow the exhaust fans to remove smoke

B.extinguish the fire by carbon monoxide smothering

C.prevent additional oxygen from reaching the fire

D.protect fire fighting personnel from smoke