There are some dangerous fishes in this river, and I've warned Jack _____

here.    [ ]

A. not to swim    

B. to not swim   

C. swim not to    

D. to swim not

在超声评分胎盘成熟度中，0级胎盘绒毛膜板表现为()

A．有弥散性暗区

B．有稠密的线状回声

C．有不完全的分叶

D．光滑，平整

E．与基底层有切迹状的交通