1、Order were given that thw attack _____ on Mcrch 1.
A.be startedB.must be started
C.had to be started D.would be started
2、With a little more care you ____ this serious mistake.
A.could avoidB.would avoid
C.could have avoidedD.must have avoided
3、It;s demanded that we ____ there on foot.
A.don't goB.not go C.not to goD.won't go
高手详细解释下，谢谢。。
