be to do 的用法
“be to do”这个结构有两种语法意义，○1连系动词be+动词不定式做表语，○2be to是一个独立词汇单位,具有情态含义,可以把它叫做情态习语(modal idiom)。
The problem is to find a solution.
His plan is to clean the room.
My wish is to be a doctor.
二、be to +动词不定式中的be to用作情态习语,这时的be to do表示: “计划”、“安排”、“义务”、“应该”、“可能”、“命运”等。(have to, ought to)。如: He is to have a holiday. (表示将来)
The committee is to meet today. (表示计划、安排)
You are to go to the hotel where rooms have already been booked for you.
1.表示“将”、“计划”、“安排”。(意思接近于be going to)如：
Their daughter is to get married soon.
Who is to question him？
It was the last film at the cinema，which was to close next day.
After dinner they were to go to a movie.
was/ were to do表示过去曾经计划要做的事，或者过去应当做的事，而且从现在的角度来看已经实现了。如：
I felt nervous because I was soon to leave home for the first time.
I was to play Juliet.
The expedition was to start in a week’s time.
was/ were to have done,表示“本打算”、“本计划”或“本应当”做的事而没有做成或没有发生。如:
I was to have seen him last Wednesday, but he didn’t come.
We were to have been married last year.
2.表示“义务”、“应该” 。(意思接近于should，must，ought to，have to)如：
No one is to leave the building.
You are not to smoke in this room.=You are not supposed to smoke in this room.
You are to be back by 10 o’clock.
Such books are to be found in the library.
Not a single sound was to be heard.
Not a soul was to be seen.
She was nowhere to be found.
She was never to see his wife and family again.
He came to power, but he was to play dearly for it: soon he was assassinated.
The worst is still to come.
They said goodbye, little knowing they were never to meet again.
6.用于“if…were to do”，表示虚拟语气。如：
If it were to rain tomorrow, the sports meeting would be put off.
1.This film ___A__ this Sunday.
A. is going to show
B. is showing
C. is to be show
D. will have been show
2.The students were told that they __C__ at the school gate at 2:00 the following afternoon.
B. will meet
C. were to meet
D. were met
3. The house ___D___ ready today but as there has been a builders’ strike it is still only half finished.
B. was to be
D. was to have been
4.In such dry weather, the flowers will have to be watered if they ___B______.
A. have survived
B. are to survive
C. would survive
D. will survive
5.How ____A___ I ______ what has become of him?
A. am; to know
B. am; knowing
C. was; to know
D. will; know
6. ___A___ he ________ tomorrow, I would go to meet him at the station.
A. Were; to come
B. Was; coming
C. Did; come
D. Would; come
该句相当于If he were to come …虚拟语气