be+不定式动词
be+不定式动词”在不同情况下，可以表示很多种不同的语义。

下面便是其中九种：
一、表示坚决的命令。

例如：
1. This naughty boy is to stay here until the class is over.
2. No one is to enter this building without the permission of the security guard.
二、表示计划”或安排的事项”例如：
3. Betty is to be married soon.
4. An in sura nee age nt is to meet us this after noon.
三、表示可能性”例如：
5. Are you to pay the debt for your wife?
6. The lovely puppy is no where to be found.
四、表示意图”或打算”例如：
7. If you are to be there on time, you had better hurry.
8. If all of us are to rema in frie ndly, we must be sin cere with one ano ther.
五、表示应该”例如：
9. You have done so well. You are to be rewarded.
10. Such n asty questi ons are to be avoided.
六、表示不可避免”例如：
11. Anne was won deri ng what was to become of her boy frie nd. Tommy.
12. The murderer was senten ced to life impris onment and was n ever to see his family aga in.
七、表示假设”例如：
13. If I were to do it, I would do it well.
14. Even if you were to take a taxi now, you would not be able to arrive at your destination on time.
八、有期待将来”的含意。

例如：
15. The actual usef uln ess of the n ewly inven ted equipme nt is still to be
determ in ed.
16. Hen ry's appo in tme nt with the acco untancy firm is yet to be con firmed.
九、有必然会发生”的含意。

例如：
17. She did not think too much of her unkind acts. However, they were to be harmful to herself, too.
18. Tom was n't worried about his head injury, but it was to be troublesome for him later.。