Unit 4: Modals – Ability, Obligation & Advice
Theory: Understanding Modals
Modal verbs help us express ability, advice, obligation, andpossibility. They never change form (no ‘s’ in the third person) and are followed by the infinitive without ‘to’ [1, 2].
1. Ability and Possibility: Can, Could, To be able to
Can expresses ability (e.g., He can carry the bag) or likelihood (e.g., It can rain sometimes). It is also used with verbs of perception like see or hear (e.g., I can see Sarah coming).
Could is used for past ability or possibility.
To be able to is used for specific achievements or when a modal form doesn’t exist (e.g., I will be able to).
2. Advice: Should and Ought to
We use should and ought to to say something is the right thing to do (e.g., You should see that film; You ought not to eat so much) [5, 6]. They can also express probability (e.g., The train should arrive soon).
3. Obligation: Must and Have to
Must indicates a strong obligation or necessity coming from the speaker (e.g., You must wash your hands).
Have to often indicates an external obligation (e.g., You have to finish the assignment).
Mustn’t means something is forbidden, while don’t have to or needn’t means there is no obligation (it is optional) [2, 7].
Exercises
Exercise 1: Multiple Choice – General Modals
Choosethe correct option to complete the sentences [8, 9].
1. I am a bit lost. (Could / Should / Must) you help me, please?
2. You (must / would / could) be over eighteen to ride a motorbike.
3. That’s a great book. You (shouldn’t / should / might) read it.
4. There are a lot of cars. He (should / shouldn’t / can) drive so fast.
5. My brother (can / should / must) count until he was six, but he is an accountant now.6. You (should / can / could) put the rubbish in the bins over there.
7. (Can / Should / Must) I leave the room? I need to make a call.
8. It is a big park. You (can / should / must) run or cycle here.
Exercise 2: Ability and Perception
Fill in the blanks with can, can’t, could, couldn’t or be able to [3, 9].
1. I ______ see Sarah coming down the street.
2. Jenna has always ______ get work, despite not having many qualifications.
3. My daughter ______ say the alphabet when she was three.
4. ______ you swim when you were five?
5. Do you think you will ______ finish the project by tomorrow?
6. I ______ carry on working; Iam exhausted!
7. We ______ hear the music from the party last night.
8. He ______ play the guitar very well.
Exercise 3: Necessity and Absence ofNecessity
Complete the sentences using must, mustn’t, have to, or don’t have to [2, 10].
1. You ______ smokein the elevator; it is forbidden.
2. You ______ finish the assignment by tomorrow; it is the deadline.
3. We ______ go now, or we might get stuck in traffic.
4. You ______ do the homework if you don’t want to; it is optional.
5. You ______ bring your bike; it is not that far to walk.
6. It is importantto rest. You ______ do anything for a few days.
7. You ______ wash your hands before eating.
8. I’m sorry, you can’t see the doctor today. You ______ make an appointment.
Exercise 4: Advice and Recommendation
Rewrite the sentences using should, shouldn’t, or ought to [11, 12].
1. It is a good idea for you to study instead of watching YouTube.
2. It is not good for the childrento eat so much ice cream.
3. I advise you to help your mum wash the dishes.
4. It is desirable that the train arrives soon.
5. He implies an expectationto pass the exam because he is intelligent.
6. It isa good thing to go and see that film.
7. Going to see the doctor would be a really good idea.
8. You look tired; I advise you to get some sleep.
Exercise 5: Correct the Mistakes
Find and correct the error in each sentence [13-15].
1. You must to wash your hands before eating.
2. He can to carry the bag.
3. You don’t have to walk on the grass; it is forbidden.
4. I would to like a coffee.
5. She ought go to the doctor.6. Do you can swim?
7. You mustn’t bring your bike, it’s not necessary.
8. We should to go now.
Exercise 6: Mixed Modals Gap Fill
Fill in the blanks with the most appropriate modal verb [16, 17].
1. ______ you make banh chung? Yes, I can.
2. You ______ respect your parents and teachers.
3. ______ I look at this album?
4. You ______ put the rubbish in the waste bins.
5. All car engines ______ be switched off at petrol kiosks.
6. ______ you help me, please?
7. Rick ______ listen to our advice.
8. ______ your brother usually come back home at Tet?
