主动词的半助动词和主动词

Question

如题所述

Answer 1

半助动词在功能上介于主动词和助动词之间，本身有词汇意义，可分为三类：
a.以be为中心成分，如：
be about to　 be going to
be bound to 　be able to
be due to　 be sure to
b.以have为中心成分，如：
had better/best　 have got to
have to
c.以seem等为中心成分，如：
seem to 　 turn out to be
appear to 　 fail to
happen to 　 tend to
2.半助动词既可是限定形式（体现时态，语态特征），也可是非限定形式（不定式或现在分词）。半助动词后的主动词都用带to 的不定式，这种不定式可以是一般形式、进行式或完成式，如：
He appears to have many friends.他似乎有许多朋友。
He seems to be enjoying himself at the party.在聚会上，他看起来很快乐。
Now，I‘m having to take a bus.现在，我不得不坐公共汽车。
You are supposed to have finished your term paper by Sunday evening.在周日晚上，你应该已经做完了你的学期论文