问题
选择题
I was trying to pick up my hat that __________ off in the wind, but failed at last.
A. had been blown . is blown C. blown D. it had been blown
答案
A
题目分析：考查定语从句和被动语态，本题中的that是一个定语从句的关系代词，指代先行词my hat在句中做主语，my hat与blow off之间构成被动的关系，使用使用被动语态。D项多了it。
点评：本题的关系代词指代先行词在句中做主语是不能省略的，另外要根据句子的意思来确定是肯定的形式还是否定的形式。