Modals — Obligation and Necessity

Reference

Common mistakes

1. You must to wear a seat belt. → You must wear a seat belt.
   no to after must
2. You mustn't bring food — but you can if you want. → You don't have to bring food.
   not necessary = don't have to
3. I must leave early yesterday. → I had to leave early yesterday.
   past → had to
4. She don't have to work on Saturdays. → She doesn't have to work on Saturdays.
   he / she → doesn't have to

Modals — Obligation and Necessity — Exercises

Choose the correct modal

Circle the best option for each sentence.

1. You don't have to / mustn't use your phone in the library. (mustn't / don't have to)
2. We don't have to / mustn't hurry. We have plenty of time.
3. You don't have to / mustn't answer the phone while driving. (mustn't / don't have to)
4. Don't you think we should / must call mum to say we'll be late?
5. A fireman has to / should wear a uniform when at work.
6. You shouldn't / mustn't go out in the rain without an umbrella.

Correct the mistakes

Each sentence has one mistake in the underlined part. Type the corrected form.

1. I must go to work by bus yesterday. My motorbike was being repaired.
    
2. You don't look well. You should to go home.
    
3. My father is a taxi driver and he should work nights. (It's part of his job.)
    
4. You don't have to play football here. It says no ball games.
    
5. People mustn't use their phones when they are talking to you.
    

Modals — Obligation and Necessity — Answer Key

Choose the correct modal

1. mustn't — Using phones is not allowed in a library → mustn't.
2. don't have to — Hurrying is not necessary — we have time → don't have to.
3. mustn't — It is against the law → mustn't.
4. should — A suggestion, not a rule → should.
5. has to — A rule of the job → has to. Should would only be advice.
6. shouldn't — Advice, not a law → shouldn't.

Correct the mistakes

1. had to go
2. You should go
3. he has to work
4. mustn't play
5. correct