775.I ________ through that bitter period without your generous help.
A.couldn't have gone
B.didn't go
C.wouldn't go
D.hadn't gone
776.You _________ buy a gift,but you can if you want to.
A.must
B.mustn't
C.have to
D.don't have to
775.答案是A;考查虚拟语气的用法。根据that bitter period暗示过去的时间，推断对过去的虚拟，故选A。
776.答案是D;don't have to没有必要=needn't;而mustn't不可以，禁止。
