—Dad, must I become a doctor like you when I finish university in the future?
—No, you________. You can make your own decision and do whatever you like.
don’t have to
can’t
mustn’t
couldn’t
Chinese is one of ______ subjects in our school.
I was watching TV ______ my mother was writing an e-mail to her friend.
We must study hard so that we can get a good job when we ________.
David worked _______ a waiter in a restaurant in his part-time.
_______ she is in trouble, her friends will help her out.