英语句子语法小问题

英语句子语法小问题
1.Our teacher told us to read books written by such masters asMao Dun and Ba Jin.
中的written by 不是用了非谓语吗?
那么这句：错：last week ,i read an interesting story taken place during wwII
对：last week ,i read an interesting story that had taken place during wwII
中的taken place 为什么是错的?
2.When I was a small boy,I would often sit for hours playing with the few toys I had.
为什么用would often sit 不可以用had often sat?
3.Before I came,I had imagined college was a paradise where I could relax after the stressful three years of high school.
为什么可以用had imagined college was a paradise 而不能用would be?
例句：Before I came to / entered college,I had
never though life at college would be so
rich and interesting
4.If the global warming continued,these islands woulddisappear.
中的l warming continued 是什么语法?
5.If I had a million yuan,I would buy my parents anapartment.
中为什么要用had?
6.I shouldn’t have lied to her in the first place.
中为什么不用 at first?
各位亲可能觉得以上问题有点傻
因为本人很久没碰过英语了
有些语法忘记了