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

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.
再问： 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
再答： 这无关紧要。