--My father ___________ a letter yesterday, but I’m not sure if he has finished it.

---Why not ask him about it ?

A．wrote

B．was writing

C．has written

D．writes

空泡样脊髓病的特征性症状是（）。

A.小脑性共济失调

B.早期出现的痛觉异常

C.进行性痉挛性截瘫

D.早期出现的触觉异常

E.感觉性共济失调