1. We haven't got much time. We (must / mustn't) hurry.
must
mustn't

2. We've got plenty of time. We (mustn't / don't need to) hurry.
mustn't
don't need to

3. I have to talk to Gary. I (must / mustn't) remember to call him.
must
mustn't

4. I have to talk to Gary. I (mustn't / needn't) forget to call him.
mustn't
needn't

5. There's plenty of time for you to make up your mind. You (mustn't / don't need to) decide now.
mustn't
don't need to

6. We (needn't / mustn't) wash these tomatoes. They've already been washed.
needn't
mustn't