I was trying to pick up my hat that off in the wind but failed at last.A. had been blown

问题补充：

I was trying to pick up my hat that off in the wind, but failed at last.

A. had been blown . is blownC. blown D. it had been blown

答案：

解析：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。