Modals of Obligation: B1 Exercises

Every answer with the reason behind it. Read the explanation for the ones you got right as well — that is where you find out whether you were right for the right reason.

Multiple choice questions — answers

1. All passengers ___ show a valid ticket at the barrier. → must

Must states a firm requirement, standard in official regulations.

2. I ___ wear a suit at work — the dress code is casual. → don't have to

Don't have to means the obligation does not exist, which is what a casual dress code means.

3. You ___ tell anyone about this. It is strictly confidential. → mustn't

Mustn't is a prohibition: the action is forbidden, not merely unnecessary.

4. Yesterday I ___ work until nine to finish the accounts. → had to

Must has no past form, so past obligation is expressed with had to.

5. What is the difference between 'must' and 'have to'? → Must is usually the speaker's own view, have to comes from outside

Must expresses internal necessity; have to points at an external rule or authority.

6. The lights are off, so they ___ be out. → must

Must also expresses confident deduction: the evidence leaves no other conclusion.

7. She ___ be at the office — I saw her leave an hour ago. → can't

Can't is the negative of deductive must. Mustn't would mean she is forbidden to be there.

8. You ___ bring anything to the party — everything is provided. → needn't

Needn't removes the necessity without forbidding anything.

9. Which sentence forbids something? → You mustn't park here.

Only mustn't is a prohibition; the other three simply say parking is not required.

10. Do I ___ pay in advance? → have to

Must cannot form a question with do. Have to behaves like an ordinary verb and can.

11. Employees ___ to complete the safety course before starting. → are required

Be required to is the formal passive alternative to must in written regulations.

12. He ___ have missed the train — he left the house at six. → must

Must have plus a past participle is a confident deduction about a past event.

13. We ___ hurry. The film does not start for an hour. → don't need to

There is no necessity, so don't need to is right; mustn't would forbid hurrying.

14. In the past, women ___ ask permission to open a bank account. → had to

A past external obligation is always had to.

15. You ___ have paid — I had already covered the bill. → needn't

Needn't have plus a participle means the action was done but was unnecessary.

16. 'I didn't need to buy milk' most naturally means ___. → There was no need, so I did not buy it

Didn't need to usually implies the action never happened; needn't have implies it did.

17. Visitors ___ leave their bags in the cloakroom. → must

Must is a modal: no to, no s, no auxiliary.

18. There ___ be some mistake — this cannot be my bill. → must

Must expresses the speaker's certainty in the face of evidence.

19. Next year we ___ move office because the lease ends. → will have to

Must has no future form either, so will have to carries future obligation.

20. She ___ be very wealthy, judging by that house. → must

Deductive must draws a confident conclusion from visible evidence.

Fill-in-the-blank questions — answers

1. You ___ wear a helmet on this construction site. → must

Must states a firm safety requirement.

2. We ___ have to book — the restaurant is never full on Mondays. → don't

Don't have to removes the obligation rather than forbidding the action.

3. You ___ touch that switch under any circumstances. → mustn't

Mustn't is a prohibition, not an absence of necessity.

4. Last winter we ___ to cancel three flights because of the snow. → had

Must has no past form, so past obligation uses had to.

5. The kitchen light is on, so somebody ___ be home. → must

Must draws a confident conclusion from the available evidence.

6. That ___ be Sarah — she is still in Australia. → can't

Can't is the negative of deductive must.

7. You ___ bring a towel; the hotel provides them. → needn't

Needn't removes the necessity without forbidding anything.

8. ___ I have to fill in this form as well? → Do

Have to forms questions with do, unlike must.

9. All staff ___ required to attend the briefing. → are

Be required to is the formal written alternative to must.

10. He ___ have taken the wrong turning somewhere. → must

Must have plus a past participle is a confident deduction about the past.

11. We ___ rush — there is plenty of time before the show. → needn't

No necessity exists, so needn't is right and mustn't would be wrong.

12. In those days everybody ___ to carry an identity card. → had

Past external obligation always takes had to.

13. You ___ have washed those — the machine does it automatically. → needn't

Needn't have means the action was carried out but was not necessary.

14. Next month I ___ have to renew my passport. → will

Must has no future form, so will have to carries future obligation.

15. Candidates ___ not use a calculator in this section. → must

Must not states a formal prohibition in exam regulations.

16. She ___ to leave early because her train was cancelled. → had

A past necessity forced by circumstance takes had to.

17. There ___ be some explanation for these figures. → must

Must expresses the speaker's certainty that a reason exists.

18. You really ___ to see that exhibition before it closes. → ought

Ought to gives a strong recommendation short of an obligation.

19. Do we ___ to pay a deposit in advance? → have

Have to is an ordinary verb here and takes do in questions.

20. The keys are gone, so he ___ already left. → must have

Must have plus a participle deduces a completed past action from present evidence.

Sentence structure: word ordering — answers

1. State a firm rule at an entrance. → All visitors must sign the register.

State a firm rule at an entrance.

2. Remove an obligation politely. → You do not have to come if you are busy.

Remove an obligation politely.

3. Forbid something outright. → You must not open that door.

Forbid something outright.

4. Describe a past necessity. → We had to wait three hours for a taxi.

Describe a past necessity.

5. Deduce something from the evidence. → He must be exhausted after that journey.

Deduce something from the evidence.

6. Reject a possibility confidently. → That cannot be the right address.

Reject a possibility confidently.

7. Say something is unnecessary. → You need not bring your own equipment.

Say something is unnecessary.

8. Ask about an obligation. → Do I have to book a seat in advance?

Ask about an obligation.

9. Word a rule in formal passive style. → Staff are required to wear identity badges.

Word a rule in formal passive style.

10. Deduce a past action from evidence. → She must have left her phone at home.

Deduce a past action from evidence.

11. Express a future obligation. → We will have to find another supplier.

Express a future obligation.

12. Say something was done unnecessarily. → You need not have paid for the tickets.

Say something was done unnecessarily.

13. Write an exam prohibition. → Candidates must not communicate during the exam.

Write an exam prohibition.

14. Describe a historical obligation. → In those days children had to work.

Describe a historical obligation.

15. Insist that a reason exists. → There must be an explanation for this.

Insist that a reason exists.

16. Recommend something strongly. → You ought to renew your insurance soon.

Recommend something strongly.

17. Say a task turned out unnecessary. → We did not need to queue at all.

Say a task turned out unnecessary.

18. State a deadline imposed from outside. → Everyone has to leave by eleven o'clock.

State a deadline imposed from outside.

19. Express disbelief about a past achievement. → He cannot have finished the whole report.

Express disbelief about a past achievement.

20. Write an in-flight instruction. → Passengers must remain seated until landing.

Write an in-flight instruction.