ank married with deanifer in a le
(1) If the students don't obey the rule, they will be punished.
fdidn't 不要]
(2) IFI knew the truth, I would tell you.
thad known 不要]
(3) IfI had known the truth, I would have told you.
fknew 不要]
(4)IfI had had to do it, I would have done it then.
(5) If he had taken my advice, he would be happier now.
[bave been 不要]