take photos
sit on a desk
shout
turn off the phone
listen to the librarian
wear headphones
bring a library card
return books on time
I must ...
I must return books on time
You must ...
You must turn off the phone
We must ...
We must listen to the librarian
He must not ...
He must not sit on a desk
We mustn't ...
We mustn't shout
He must ...
He must wear headphones
They mustn't ...
They mustn't take photos
You must ...
You must bring a library card
