Modals - deduction about the past

Modals - deduction about the past

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Look at these examples to see how must, might, may, could, can't and couldn't are used in the past.

An earthquake? That must have been terrifying!

We don't know for sure that Alex broke the coffee table. It might have been the dog.

A: "I heard that Suzy got caught shoplifting yesterday afternoon"

B: "She can't have done it. She and I were at the movies all afternoon"

=> more emphatic, like a statement of fact

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A: "I heard that Suzy got caught shoplifting yesterday afternoon"

B: "She couldn't have done it. She's not that type of girl"

=> you want to believe that she didn't do it

S + must have + V-past participle

We use this when we feel sure about what happened.​

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E.g. The thief must have had a key. The door was locked and nothing was broken.

S + might / may have + V-past participle

We use this when we think it's possible that something happened. 

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E.g. I think I might have left the air conditioning on. Please can you check?

S + can't / couldn't have + V-past participle

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We use this when we think it's not possible that something happened.

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E.g. She can't have driven there. Her car keys are still here.

could have done and should have done

🔥 could have + V-past participle

=> you could do something but you didn't do it.

E.g. They could have won the race, but they didn't try hard enough.

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​🔥 should have + V-past participle

=> you should do something but you didn't do it.

E.g. John should have left early, then he wouldn't have missed the plane.

Multiple Choice

I _____ left my wallet in the restaurant. I paid for the taxi home afterwards.

• must have

• could have

• can't have

Multiple Choice

Why were there no buses yesterday? Maybe it was the snow or they _____ been on strike.

• must have

• might have

• couldn't have

Multiple Choice

You _____ seen her, surely! She was standing right in front of you.

• must have

• might have

• can't have

Multiple Choice

Let's ask at reception to see if they have your keys. Someone _____ found them.

• must have

• might have

• can't have

Multiple Choice

He _____ gone to Russia. He didn't have a passport.

• must have

• might have

• couldn't have

Multiple Choice

I explained the homework but she did the wrong page. She _____ misunderstood me.

• must have

• may have

• can't have

Multiple Choice

Oh no! My phone's not in my bag. I _____ left it at home.

• must have

• can have

• couldn't have

Multiple Choice

It is still a mystery how the robber gained access to the bank. Police are investigating whether the suspect _____ known one of the employees.

• must have

• may have

• couldn't have

Multiple Choice

Where's Clare? Her bag's here and her computer's still on so she _____ gone home.

• must have

• might have

• can't have

Multiple Choice

I can't remember my password! But I _____ written it in my notebook as sometimes I do that.

• must have

• may have

• couldn't have

Multiple Choice

He wasn't answering the phone before. Maybe he went to the shop or he _____ been in the shower.

• must have

• might have

• couldn't have

Multiple Choice

Sorry, I don't know if she's here or not. She was feeling ill so she _____ gone home.

• must have

• might have

• can't have

Multiple Choice

She _____ cleaned the whole house on her own in two hours. She must have had some help.

• must have

• might have

• can't help

Multiple Choice

Wow! Have you finished all that already? You _____ been hungry!

• must have

• may have

• can't have

Multiple Choice

He _____ known about it when I saw him. I'm sure he would have told me.

• must have

• might have

• couldn't have

Multiple Choice

Oh, great! His car's here. He _____ come home earlier than planned.

• must have

• might have

• can have

Poll

Are you confident with modal verbs?

• I'm good

• I still need more practice