Grammar » B1 Grammar lessons and exercises » Modal verbs of deduction – must, may, might, could, can’t
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  • Modal verbs of deduction – must, may, might, could, can’t

    Exercise 1

    Choose all the correct modal verbs of deduction for each gap below. In some sentences there are TWO possible correct answers.

    Page 1 of 2

    1 Paul is behaving in a very unusual way. I think he ______ again.
    a.
    b.
    c.
    2 I think there ______ a mistake in your tax return. You should check it. Choose TWO correct options
    a.
    b.
    c.
    3 If Suzan said that, it ______ true. She never lies.
    a.
    b.
    c.
    4 Sorry, but I'm not Connor. You ______ me for someone else.
    a.
    b.
    c.
    5 I'm not sure I trust Peter. He ______ the person we think he is.
    a.
    b.
    c.

     

  • Modal verbs of deduction – Grammar chart

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    May, might

    We use may and might to talk about things that are possibly true, but we don’t know for sure.

    • He’s more than 2 meters tall. He might be a basketball player. (=perhaps he is)
    • He says Betty is his friend, but I think she may be his girlfriend.

    We use may not or might not to talk about things that are possibly not true, but we don’t know for sure.

    • You should call her. She might not know where you are. (=perhaps she doesn’t know)

    Don’t use can for deduction

    We don’t use can as a modal of deduction.

    • He can be at home now.
    • He might/may be at home now.

    Must, can’t

    We use must when we are sure, or quite sure, that something is true.

    • You must be tired after the long journey. (=I’m sure you are tired)
    • I’m sure I had the keys when I left. They must be in the car.

    But we use can’t (NOT mustn’t) when we are sure, or quite sure, that something is not true.

    • We’ve been walking for hours. It mustn’t be far from here.
    • We’ve been walking for hours. It can’t be far from here. 
    • They’ve lived here only for a couple of months. They can’t know many people.

    + be + -ing

    After may, might, must or can’t, we can use be + -ing, when we are talking about actions in progress.

    • They’ve gone to Ibiza, and right now, they must be having a great time.
    • Call him. He might be waiting for us.
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