通常不损害脊髓后索的疾病是

A．亚急性联合变性 

B．脊髓结核 

C．Friedreich共济失调 

D．糖尿病性脊髓病 

E．肌萎缩侧索硬化症

If a davit-launched life raft aboard a vessel cannot be launched because of damage to the davit，you should（）.

A.inflate the life raft on deck

B.roll the life raft over the side

C.go to another life raft station

D.get a saw and cut the life raft free