Поговорим по-английски!

I have today a topic: mustn't be, must be, don't have

Не точно понял что ты хочешь знать...извени

но например, предложение:
-It must be cold outside if the water froze.
-The sky is getter lighter, it mustn't be long now until morning.
-I don't have time to eat because I have to be at work in 10 minutes.

мм...полезно?