It is difficult to memorize English new words,isn't it?

问题描述:

It is difficult to memorize English new words,isn't it?
Not necessarily.____ them repeatedly and you will find it easier to memorize them.
A.Seeing B.Seen C.To see D.See
which one?why?

答案为:D.此句属于:祈使句+陈述句.相当于If you see them repeatedly,you will find it easier
to memorize them.又例:Work hard and you will succeed.因为原来看到的祈使句+陈述句,在and前面都有",", 这句没有,所以就不确定了这无关紧要。