1,When supply is more than demand ______ any product,prices

1,When supply is more than demand ______ any product,prices are timely to fall.
A,for
B,with
C,about
D,to
为什么选A
2,It's wrong for ______ parent to tell kids to ignore what the other parent tells them to do.
A,each
B,either
C,every
D,both
为什么选B不选D
3,Intelligent people need never work hard to be successful in the field where they are engaged in,______ they?
A,needn't
B,don't
C,do
D,need
为什么选D,什么情况下有need的时候选C
4,Earlier fears about the weather disappeared when the rain which had been forecast ______ to appear.
A,would fail
B,fails
C,failed
D,has failed
这句话我没看懂诶= 能帮我翻一下么?还有为什么答案是选C
5,I really regret ______ you the fact that your school team lost the game just this morning as you feel so upset.
A,tell
B,telling
C,to tell
D,told
为什么答案选B,不是一般都是regret to say,regret to tell的么?