Language point: should, must, have to
4 Look at sentences 1-5 and read the
rules. Then change the words in blue
using your own ideas.
1 You shouldn't smoke. It's dangerous.
2 You mustn't take drugs. It's illegal.
3 You don't have to diet. It isn't healthy.
4 You have to give your opinion.
5 The message should be clearer.

O RULES
a We can use must / have to to express obligation
b We use should / must to express advice.
C We use mustn't to express prohibition.
d We use don't have to to express a lack of obligation.​