MUST / MUSTN'T
must
Where are you?
Were you at home yesterday? (yes)
Yes, I was.
mustn’t
What is your name?
Were you at school yesterday? (no)
No, I wasn’t.
must
Where do you live?
Did you watch TV last night? (no)
No, I didn’t
mustn’t
What are you doing?
Did you do your homework? (yes)
Yes, I did.
must
What is your favourite subject?
Have you ever been to London? (no)
No, I haven’t.