1.the river smells terrible.people must ( )dirty things into

1.the river smells terrible.people must ( )dirty things into it.
A.be stopped to throw
B.be stopped (from) throwing.[我记不到原题是不是有from,我问的是语法.把这个打出来希望有帮助]
C.stop to throw
D.stop from throwing
2.not ...enough [for sb] to do sth是固定搭配吗?
是不是可以用of sb?关于两个的具体用法呢?
3.unless用法和if ...not...完全一样吗?
速求!请详尽明了,选什么,不选什么的原因,用到的语法都请告诉我,..
1.那为什么不能用be stopped doing sth 或stop from doing sth？
2、表示1楼同胞您说的那个人的本性是OF SB。我问的是某人不足够做某事的用法啊。
3.难道you will be tired if you don't sleep.和
you will be tired unless you sleep