情态动词加do还是to
情态动词加do还是to do？
do？
情态动词加do，do为动词原形，详解如下。
动词原形是指使用英语时动词本身的形态，即与助动词或情态动词do，does，did，shall，will，should，would，may，might，can，could，must，need，ought to等一起构成谓语的动词时，要用原形。与助动词或情态动词do, does, did, shall, will, should, would, may, might, have to, must, need, ought to等一起构成谓语的动词时，要用原形。
will have to do这个句型，will和have to不都是情态动词吗?为什么能同时出现？
will 是表示将来时态。
have to do是动词短语 “不得不做”的意思。
连起来表示 将来不得不做什么事情 。
had to do是谓语吗？
是谓语
如：
Fifteen policemen had to push very hard to get him off the main street
He had to look after his sister yesterday.他昨天不得照顾他的妹妹。
谓语为：had to ……属于“情态动词 动词原形”构成复合谓语
又如：
We have had to turn down four applicants already. 我们已经不得不回绝了四位申请人
have to 相当于情态动词 must
have to 动词原形 共同做谓语
如：
We have to take umbrellas when it is rains
have to do的非限定形式：
He has had to do his homework. had为过去分词。
To climb the rock face, we had to take various precautions
谓语 had to take 的目的—— “ 为了爬过 the rock face ” 。