must. mustn't. don't have to
I've told you befoe - you ______ play football in the street.
You____ forget to lock the door before you leave.
If you go to London. you _____ go to the Trocadero - it's great!
My old dictionary is useless - I ____ buy a new one

I've told you before - you mustn't play football in the street.You don't have to forget to lock the door before you leave.If you go to London you must go to the Trocadero - it's great!My old dictionary is useless - I must buy a new one