01a strong positive deduction from evidence, not an imposed obligation
Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation.
They must be at home.B1
Present deduction with modals Exercises
About this lesson
Present deduction with modals · B1. Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation.
Complete 12 original tasks. Use the situation to choose the intended meaning, practise the form, then apply it in a fresh context.
12 items
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Knowledge map
Start practisingPresent deduction with modals
02a conclusion that something is impossible based on contradictory evidence
Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence.
She can’t be in Oslo.03an uncertain possibility; the evidence does not justify certainty
Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty.
The parcel might be at the reception desk.Illustrated guide
01 / 12D01Save it to find it in My collection.
All the lights are on and music is playing; make a strong positive deduction.
They ___ be at home.
Your learning route
01
Step 1 · Warm-up
0/3Warm-up
02
Step 2 · Build the skill
0/2a strong positive deduction from evidence, not an imposed obligation
Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation.
They must be at home.03
Step 3 · Build the skill
0/1a conclusion that something is impossible based on contradictory evidence
Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence.
She can’t be in Oslo.04
Step 4 · Build the skill
0/1an uncertain possibility; the evidence does not justify certainty
Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty.
The parcel might be at the reception desk.05
Step 5 · New contexts
0/3New contexts
06
Step 6 · A fresh challenge
0/2A fresh challenge
Practice notes in this unit
0Make mistakes useful.
Keep the first try. Understand the change. Check it in a fresh situation.
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Lesson map
B1Present deduction with modals
Lesson points
a strong positive deduction from evidence, not an imposed obligation
Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation.
They must be at home.a conclusion that something is impossible based on contradictory evidence
Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence.
She can’t be in Oslo.an uncertain possibility; the evidence does not justify certainty
Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty.
The parcel might be at the reception desk.Questions & answers
Opening an answer records help for that question.
All the lights are on and music is playing; make a strong positive deduction.
They ___ be at home.
- mustn’t
- can’t
- must
- should have
Answer & explanation
must
Look at “They ___ be at home.”. Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation. Complete sentence: “They must be at home.”.
I am speaking to her in Lisbon right now, so being in Oslo is impossible.
She ___ be in Oslo.
- must
- can’t
- has to
- mustn’t
Answer & explanation
can’t
Look at “She ___ be in Oslo.”. Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence. Complete sentence: “She can’t be in Oslo.”.
Other accepted versions
- can't
There is a possible explanation, but we have no confirmation.
The parcel ___ be at the reception desk.
- can’t
- might
- must
- mustn’t
Answer & explanation
might
Look at “The parcel ___ be at the reception desk.”. Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty. Complete sentence: “The parcel might be at the reception desk.”.
Fresh footprints lead from the only door; make a strong positive deduction.
Someone ___ be inside.
- mustn’t
- can’t
- should have
- must
Answer & explanation
must
Look at “Someone ___ be inside.”. Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation. Complete sentence: “Someone must be inside.”.
The car is in the locked garage and I have the only key. Express a strong deduction that the car outside is not mine.
That car outside ___ be mine.
Answer & explanation
cannot
Complete sentence: “That car outside cannot be mine.” Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence. The subject, time and meaning in the task determine this form. Only reviewed responses are matched automatically; other wording is not automatically wrong.
Other accepted versions
- can't
- can not
Express uncertain possibility; there is no decisive evidence.
The noise ___ be a loose window.
- can’t
- must
- mustn’t
- could
Answer & explanation
could
Look at “The noise ___ be a loose window.”. Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty. Complete sentence: “The noise could be a loose window.”.
Express a strong positive deduction, not an order.
You ran twenty kilometres; you ___ be exhausted.
Answer & explanation
must
Complete sentence: “You ran twenty kilometres; you must be exhausted.” Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation. The subject, time and meaning in the task determine this form. Only reviewed responses are matched automatically; other wording is not automatically wrong.
The label and sealed transparent packaging show that this is the correct part.
This ___ be the replacement we ordered.
- can’t
- should have
- mustn’t
- must
Answer & explanation
must
Look at “This ___ be the replacement we ordered.”. Use must + base verb to express a strong positive deduction from evidence, not an imposed obligation. Complete sentence: “This must be the replacement we ordered.”.
Express impossibility: this machine has no power supply.
It ___ be running now.
Answer & explanation
cannot
Complete sentence: “It cannot be running now.” Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence. The subject, time and meaning in the task determine this form. Only reviewed responses are matched automatically; other wording is not automatically wrong.
Other accepted versions
- can't
- can not
The office could be closed, but we do not know. Choose an uncertain modal.
The staff ___ be on a lunch break.
- mustn’t
- can’t
- may
- must
Answer & explanation
may
Look at “The staff ___ be on a lunch break.”. Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty. Complete sentence: “The staff may be on a lunch break.”.
The witness is with us now, so being at the airport is impossible.
He ___ be at the airport.
- must
- can’t
- has to
- mustn’t
Answer & explanation
can’t
Look at “He ___ be at the airport.”. Use can't + base verb to express a conclusion that something is impossible based on contradictory evidence. Complete sentence: “He can’t be at the airport.”.
Other accepted versions
- can't
Keep the deduction uncertain rather than presenting it as established fact.
The unfamiliar caller ___ be a new client.
Answer & explanation
might
Complete sentence: “The unfamiliar caller might be a new client.” Use might/may/could + base verb to express an uncertain possibility; the evidence does not justify certainty. The subject, time and meaning in the task determine this form. Only reviewed responses are matched automatically; other wording is not automatically wrong.
Other accepted versions
- may
- could