Modals of deduction (B2) — English exercises with answers

Must, might, could and can't for logical certainty, possibility and impossibility about present and past situations

Correct answers are marked. Add the set to your exercises to open it in the editor, where you can adjust tasks, play them on screen or add them to a lesson.

1
Multiple choice
The lights are off and the car isn't outside. They be out.
mustcan'tshouldneedn't'Must' expresses strong certainty based on evidence.
2
Multiple choice
He's not answering his phone. He be in a meeting.
mightmustcan'tshould'Might' expresses a possibility, not a certainty.
3
Multiple choice
She knows every street in the city. She have lived here a long time.
mustcan'tmustn'tshouldn't'Must have' + past participle expresses certainty about a past situation.
4
Multiple choice
He got a perfect score without studying at all. That be true!
can'tmustmightcould'Can't' expresses that something is logically impossible.
5
Fill the gap
You've been travelling all day. You be exhausted.
Answer: must'Must' + infinitive expresses a strong logical conclusion about the present.
6
Fill the gap
There's a light on in the office. Someone still be working.
Answer: mustWe use 'must' when evidence strongly suggests something is true.
7
Fill the gap
I'm not sure where he is — he have missed the train.
Answer: mightAlso accepted: may, could'Might/may/could' + have + past participle expresses a possible explanation about the past.
8
Fill the gap
She said she'd never been to Paris, but that be right — I saw a photo of her at the Eiffel Tower.
Answer: can't'Can't' + infinitive expresses something that is logically impossible.
9
Fill the gap
He have forgotten about the meeting — he never misses one usually.
Answer: must'Must have' + past participle is used for a confident guess about the past.
10
True / false
This sentence is correct: 'She must have been tired after the long flight.'
Answer: True'Must have' + past participle correctly expresses certainty about a past situation.
11
True / false
This sentence is correct: 'He mustn't be at home — all the lights are off.'
Answer: FalseA negative deduction uses 'can't be', not 'mustn't be': 'He can't be at home.'
12
Discussion question
Look around the room you're in now. What can you deduce about the person who was last there, using must/might/can't?
Sample answer: The window is open, so someone must have wanted fresh air. There's a cup on the table, so they might have been drinking tea. The light is off, so they can't still be working.

Must, might, could and can't for logical certainty, possibility and impossibility about present and past situations

Correct answers are marked. Add the set to your exercises to open it in the editor, where you can adjust tasks, play them on screen or add them to a lesson.

1
Multiple choice
The lights are off and the car isn't outside. They be out.
mustcan'tshouldneedn't'Must' expresses strong certainty based on evidence.
2
Multiple choice
He's not answering his phone. He be in a meeting.
mightmustcan'tshould'Might' expresses a possibility, not a certainty.
3
Multiple choice
She knows every street in the city. She have lived here a long time.
mustcan'tmustn'tshouldn't'Must have' + past participle expresses certainty about a past situation.
4
Multiple choice
He got a perfect score without studying at all. That be true!
can'tmustmightcould'Can't' expresses that something is logically impossible.
5
Fill the gap
You've been travelling all day. You be exhausted.
Answer: must'Must' + infinitive expresses a strong logical conclusion about the present.
6
Fill the gap
There's a light on in the office. Someone still be working.
Answer: mustWe use 'must' when evidence strongly suggests something is true.
7
Fill the gap
I'm not sure where he is — he have missed the train.
Answer: mightAlso accepted: may, could'Might/may/could' + have + past participle expresses a possible explanation about the past.
8
Fill the gap
She said she'd never been to Paris, but that be right — I saw a photo of her at the Eiffel Tower.
Answer: can't'Can't' + infinitive expresses something that is logically impossible.
9
Fill the gap
He have forgotten about the meeting — he never misses one usually.
Answer: must'Must have' + past participle is used for a confident guess about the past.
10
True / false
This sentence is correct: 'She must have been tired after the long flight.'
Answer: True'Must have' + past participle correctly expresses certainty about a past situation.
11
True / false
This sentence is correct: 'He mustn't be at home — all the lights are off.'
Answer: FalseA negative deduction uses 'can't be', not 'mustn't be': 'He can't be at home.'
12
Discussion question
Look around the room you're in now. What can you deduce about the person who was last there, using must/might/can't?
Sample answer: The window is open, so someone must have wanted fresh air. There's a cup on the table, so they might have been drinking tea. The light is off, so they can't still be working.