以下选项中，MRA检查受限制的因素是()

A．病人的耐受性  

B．金属伪影　

C．费用 

D．禁忌证 

E．以上都是

If a vessel takes a sudden severe list or trim from an unknown cause, you should first（）.

A.determine the cause before taking countermeasures

B.assume the shift is due to off-center loading

C.counterflood on the side opposite the list or trim

D.assume the cause is environment forces