Modal Verbs of Deduction – must, may, might, could, can’t

Exercises

Explanation

1. Present Modals of Deduction

Must – we are very sure something is true

Form: must + verb
Examples:

• She must be at the library; she goes there every morning.

• They must know the answer already.

Can’t – we are very sure something is impossible

Form: can’t + verb
Examples:

• He can’t be the manager; he’s too young.

• This can’t be the right key.

May / Might / Could – something is possible

Form: may/might/could + verb
Examples:

• She might be busy right now.

• They could be in the garden.

• It may be the wrong number.

2. Past Modals of Deduction

We use must have / can’t have / might have / may have / could have + V3 to guess about past events.

Must have – strong belief about the past

Examples:

• She must have left early; the house is empty.

• They must have forgotten the time.
  
  

Can’t have / couldn’t have – we are sure something didn’t happen

Examples:

• He can’t have taken the wrong bus.

• She couldn’t have seen you yesterday; she was abroad.

Might have / May have / Could have – a possible past event

Examples:

• They might have missed your message.

• He may have left his bag on the train.

• She could have lost her phone.

3. Continuous Forms

We use these to guess about an action that is/was happening over a period of time.

Present continuous deduction

• She must be working right now.

• He can’t be driving yet; he doesn’t have his license.

• They might be studying upstairs.

Past continuous deduction

• She must have been sleeping when we arrived.

• They can’t have been watching TV; it was turned off.

• He might have been cooking when the phone rang.

4. Why we use modals of deduction

These verbs help us:

• show how sure we are,

• make polite or careful guesses,

• sound more natural in real communication.

They are useful in everyday speaking, storytelling, explanations, and problem-solving.