We use modal verbs of possibility and deduction to say how sure we are about something. Must means we’re sure it’s true, can’t means we’re sure it isn’t, and might, may and could mean it’s possible. Start with the table. In the exercises below, each answer has a short explanation.
| How sure? | Present / future | Past |
|---|---|---|
| Sure it’s true | She must be tired. | She must have been tired. |
| Possible | He might / may / could be at home. | He might / may / could have left. |
| Probable | They should arrive soon. It may well rain. | It should have arrived by now. |
| Sure it’s not true | That can’t be right. | You can’t / couldn’t have seen him. |
Modal verbs of possibility quiz
Four sets of 20 questions: start with Basics (A2–B1) for the present, move on to past deduction (B1–B2) and advanced probability (C1), or try the At work set. In typed answers, a hint in brackets tells you how sure the speaker is. Prefer to check everything at the end? Switch to Exam mode.
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Take an umbrella. It rain later.
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He’s been working for 12 hours. He be tired.
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That be Tom at the door. He’s in Paris this week.
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I’m not sure where Anna is. She be in the library.
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You’ve just eaten a whole pizza! You be hungry. (I’m sure it’s not true)
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Look at her ring. She be married.
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The lights are off. They be at home.
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We go to the beach tomorrow if the weather’s nice.
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I don’t know the answer. Ask Tom. He know. (it’s possible)
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Is that her sister? She looks just like her. She be her sister.
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She not come to the party. She isn’t feeling well.
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That story be true! Pigs can’t fly.
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It’s 9 pm. The shops be closed by now. (I’m sure)
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he be at work? It’s Sunday.
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This bag is really heavy. There be books in it.
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I see you later, but I’m not sure yet.
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You be serious! You’re joking, right? (I’m sure it’s not true)
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He speaks perfect Spanish. He be from Madrid.
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Don’t touch the oven. It be very hot.
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She might late tonight.
Teachers: download these questions as a printable worksheet with an answer key. It’s free to use in class.
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The ground is wet. It rained last night.
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She didn’t answer the phone. She been asleep.
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You seen John yesterday. He was in Berlin! (I’m sure it’s not true)
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I can’t find my keys. I left them at work.
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Tom wrote the meeting in his diary and set three alarms. He forgotten about it.
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They won the match. They were playing really badly.
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She looks very happy. She (pass) her exam. (I’m sure)
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The window’s broken. Someone thrown a ball through it.
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I’m not sure why she left early. She been feeling ill.
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Where’s Dad? He (go) to the shops. The car isn’t here. (I’m sure)
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You been very worried when you lost your passport.
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It been Mike you saw. He’s been in hospital all week.
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I (leave) my phone in the taxi. I’m not sure. (it’s possible)
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He be working. His car is in the office car park.
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She be enjoying the party. She’s sitting alone in the corner.
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There’s no answer. They gone out.
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He’s wearing a suit. He (go) to a job interview. (it’s possible)
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“Where’s Lucy?” “I’m not sure. She be in the garden.”
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You got 100%! You studied really hard.
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I’m sure I locked the door. Someone else opened it.
Teachers: download these questions as a printable worksheet with an answer key. It’s free to use in class.
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She well be right, but I’d like a second opinion.
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If you leave now, you’re to catch the train.
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They left an hour ago, so they arrive soon. (it’s probable)
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He have been waiting for ages. He looks really annoyed.
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You have told me! I would have helped.
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We have won if our best player hadn’t been injured.
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She (not / see) the message yet. She hasn’t replied. (it’s possible)
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He have stolen the money: he was with me all evening.
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The film be over by now. It started three hours ago.
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There’s to be a solution to this problem. (it’s certain)
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“Who called?” “I don’t know. It have been a wrong number.”
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It’s that the meeting will be cancelled.
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They (argue). Their faces are red and nobody’s speaking. (I’m sure)
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I have gone to university, but I decided to start working instead.
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The package have arrived. I’ve been at home all day and nobody rang.
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There have been about 500 people at the concert.
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Prices are to rise again next year. (probable)
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Careful! You have hurt yourself!
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He be lying. I’ve known him for years, and he’s always honest.
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She have been driving too fast. The police stopped her.
Teachers: download these questions as a printable worksheet with an answer key. It’s free to use in class.
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The client hasn’t replied. He be on holiday.
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This report has lots of mistakes. Somebody checked it.
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The CEO has been in meetings all day. She be exhausted. (I’m sure)
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It be the printer. I’ve just replaced it.
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Sales increase next quarter if the new campaign works.
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I sent the file, but he says he didn’t get it. It (go) to his spam folder. (it’s possible)
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The office is empty. Everyone gone home.
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He be the new manager. He only started last week.
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We win the contract, but it’s not certain.
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She (work) from home today. Her laptop isn’t on her desk. (it’s possible)
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The meeting have finished. I can hear people leaving the room.
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You have sent the email to the wrong address. Check again.
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The deadline was yesterday? We (miss) it! (I’m sure it’s not true)
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The price is to go up after the merger.
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They be negotiating. The door has been closed for hours.
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We have finished on time if the supplier hadn’t been late.
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The new system be ready by Monday. (it’s probable)
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That be right. The total is much higher than last month.
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He’s to be promoted. He’s the best salesperson we have.
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I have misunderstood the instructions. Could you explain again?
Teachers: download these questions as a printable worksheet with an answer key. It’s free to use in class.
Talking about the past: modal + have + past participle
For deductions about the past, add have + past participle after the modal. For actions in progress, use be + -ing (now) or have been + -ing (past):
- The ground is wet. It must have rained.
- His car is outside. He must be working.
- She looks annoyed. She must have been waiting for ages.
Could have: possible, but it didn’t happen
Could have and might have can also describe something that was possible but didn’t happen: Careful! You could have hurt yourself! / We might have won if Tom hadn’t been injured.
Common mistakes
- ❌ He mustn’t be at home. The lights are off. → ✅ He can’t be at home. (mustn’t = it’s not allowed)
- ❌ She must to be tired. → ✅ She must be tired. (no to after modals)
- ❌ He must went home. → ✅ He must have gone home.
- ❌ Can she be at work? It’s Sunday. → ✅ Could she be at work?
FAQ
Is there a difference between might, may and could?
For possibility, they mean almost the same. May is a little more formal, and might can sound slightly less sure. In questions, use could or might (Could he be lost?), not may. In the negative, might not and may not express possibility, but couldn’t means it’s impossible.
What level are these exercises?
There are four sets: Basics (A2–B1), Intermediate (B1–B2), Advanced (C1) and At work (B1–B2). The advanced set covers may well, bound to, likely and should for probability.