Deduction & Speculation Exercises PDFSet 2: The Certainty Scale: Must, May, Might, Could & Can't Exercises
20 questions·12 min·Answers included·Explanations included
Preview: Questions
Fill in the blank with the correct option.
1.I'm not sure where Tom is. He ___ be at the library — he sometimes studies there after school.
a) mustb) can'tc) mightd) mustn't
2.The car engine is making a terrible noise. There ___ something wrong with it.
a) can't beb) must bec) might not bed) shouldn't be
3.Anna was at the gym yesterday looking perfectly healthy, so she ___ be seriously ill.
a) can'tb) mustc) shouldd) might
4.I don't know where my keys are. They ___ be in my coat pocket — I'll go and check.
a) mustb) can'tc) mustn'td) could
5.Lisa has been working 12-hour shifts all week. She ___ be completely exhausted.
a) mustb) mightc) couldd) can't
... and 15 more questions in the PDF
Preview: Answers
1.might
2.must be
3.can't
4.could
5.must
... and 15 more answers in the PDF
Preview: Explanations
1."might"(c)
Use 'might' when you are NOT sure — it expresses possibility, not certainty. The clue 'I'm not sure' and 'sometimes' tell us this is a guess, not a strong deduction. 'Must' would be too strong here.
2."must be"(b)
Use 'must be' when the evidence is strong and clear. A terrible noise from the engine is strong evidence that something is wrong. This is a strong deduction, not just a possibility.
3."can't"(a)
Use 'can't' when the evidence makes something almost impossible. She was healthy at the gym yesterday, so it's almost impossible that she is seriously ill now.
4."could"(d)
Use 'could' to express possibility — something that is possible but you are not certain about. 'I don't know' and 'I'll go and check' show this is an uncertain guess. 'Must' would be too strong here.
5."must"(a)
Use 'must' when the evidence is very strong. Working 12-hour shifts all week is strong evidence of exhaustion — we can be almost certain about this conclusion.
... and 15 more explanations in the PDF
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