有几道英语题目需详细解释,谢谢

有几道英语题目需详细解释,谢谢
Millions of pounds' worth of damage by a storm which swept across the north of England last night,
A.has been caused B.had been caused 答案是C,我觉得a 也可以
2.I heard that really had a wonderful time at John's birthday party ,?
A. didn't you B.hadn't you 答案是A,但是从句中的助动词是had 为什么怒选择B呢
3.little about what others think. A.hehas cared B.he cares C.cared he D.does he care 答案是d
4.the reason she gave for not being present wasthe heavy snow prevented her coming . A./; because B.why:because C,/: that D.why:whether 答案是c