C. Complete with must/have to, mustn't or don't have to.
1. We
- pay an entrance fee. The computer
fair isn't free.
2. I'll tell you a secret, but you
tell anyone
OK?
3. Don't leave your rubbish on the beach. We
- keep it clean.
4. You
take the dog for a walk now. I'll do
it later.
5. Don't throw popcorn in the water! The sign says
that we
feed the fish!​

C. Complete with must/have to, mustn't or don't have to.

1. We don't have to pay an entrance fee. The computer fair isn't free.

2. I'll tell you a secret, but you mustn't tell anyone, OK?

3. Don't leave your rubbish on the beach. We must keep it clean.

4. You don't have to take the dog for a walk now. I'll do it later.

5. Don't throw popcorn in the water! The sign says that we mustn't feed the fish!​