Mr Smith ______ a book about China last year but I don’t know whether he has finished it.

A．has written

B．wrote

C．had written

D．was writing

小脑幕裂孔疝起因常是

A．一侧幕上占位病变
B．后颅窝占位病变
C．枕大孔区占位病变
D．椎管内占位病变
E．第四脑室肿瘤