C( 内から正しいほうを選びなさい。
1. Spectators at tennis matches (must / mustn't) be quiet.
2. Don't make so much noise. We (must / mustn't) wake the baby.
3. There were no empty seats on the bus, so we (must / had to) stand.
4. I stay up late on Friday because I (mustn't/ don't have to) work on Saturday.
5. You (mustn't/ needn't) tell Jenny. She already knows.
6. That restaurant (can't / must) be very good. It's always full of people.