Question

一般将来时中be to+动词原形，表示哪几种含义？

Answer 1

1、be + to do 表示“想，打算”，相当于intend, want。
If we are to be there before ten, we’ll have to go now.
如果我们要在十点前到，我们现在就得走。
以下是be to do sth. 作情态助动词的用法。
2、be + to do 表示按计划或安排要做的事。
When are you to leave for home?
你什么时候回家?
She is to be married next month.
她将于下个月结婚。
The Queen is to visit Japan in a week’s time.
女王将于一周后访问日本。
这种结构也可用于过去。was / were to do sth. 表示曾经计划要做的事，但并说明计划是否被执行了，所以也可表示曾经计划但未有实现的事。例如：
I felt nervous because I was soon to leave home for the first time.
我感到很紧张，因为我很快就要首次离开家了。
They said goodbye, little knowing that they were never to meet again.
他们告了别，不知道以后再也不会见面了。
We were to have told you, but you were not in.
我们本来想告诉你的，但是你不在家。
3、be + to do 表示“可以，可能”，相当于may, can。
The news is to be found in the evening paper.
这条消息可以在晚报上见到。
Such people are to be found everywhere.
这种人到处都有。
She is nowhere to be found.
在哪里也找不着她。
4、be + to do 表示“应该”，相当于should, ought to。
You are to report to the police.
你应该报警。
What is to be done?
应该怎么办呢?
5、be + to do 表示“必须”，相当于must, have to。
The letter is to be handed to him in person.
这封信必须亲手交给他。
You are to do your homework before you watch TV.
看电视之前你得先做完作业。
6、be + to do 用于否定句，表示“禁止”，相当于mustn’t。
The books in this room are not to be taken outside.
这个室内的书籍不得带出室外。
You are not to smoke in the reading-room.
你不可以在阅览室里吸烟。
7、be + to do 用于第一人称疑问句，表示征求对方意见。
Am I to go on with the work?
要我继续完成这项工作吗?
What are we to do next?
我们下一步该怎么办?
8、在虚拟语气中，不论什么人称都用were to do sth. 表示对未来的假设。
If I were to tell you that I killed him, would you believe me?
要是我告诉你是我杀了他，你会相信吗?
Even if the sun were to rise in the west, I would never do such a thing.
即使太阳从西边出来，我也决不做这种事。
9、还有两个常用的 be to do sth. 结构：be to blame(该受责备，对某坏事应负责任)，be to let(待出租)。两种结构中，用不定式的主动形式表示被动含义。
Which driver is to blame for the accident?
这事故是哪个司机的责任?
This house is to let.
这房子要出租。

Answer 2

这里to是不定式的用法,后面加动词原形,不定式除了谓语基本上其他的句子成分都可以做.助动词可以算成是独立的,不属于不定式中的动词,助动词就是帮助实义动词构成否定句疑问句的,常用的助动词有do.does.did.have.has .had,动词可以大致分为实义动词,助动词,系动词,情态动词等等,助动词就是帮助实义动词,没有实义动词就不会出现助动词.