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：
⒈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.
⒉表示“计划”或“安排的事项”。例如：
3. Betty is to be married soon.
4. An insurance agent is to meet us this afternoon.
⒊表示“可能性”。例如：
5. Are you to pay the debt for your wife?
6. The lovely puppy is nowhere to be found.
⒋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 remain friendly, we must be sincere with one another.
⒌表示“应该”。例如：
