Past modals of deduction
Use modal perfect forms to make deductions about what probably, possibly or certainly did not happen.
Learning goal: Past modals of deduction
Use must have, might have and cannot have plus a past participle.
In a nutshell
Use modal perfect forms to make deductions about what probably, possibly or certainly did not happen.
When do we use it?
Use must have, might have and cannot have plus a past participle.
Pattern
Form
Use must have for strong certainty, might have for possibility and can’t have for impossibility.
- She must have forgotten.
- They might have left.
- He can’t have seen us.
Examples
Key contrast
At B2, choose the form from the complete context: sequence, viewpoint, degree of certainty and clause structure all matter.
Watch out
Common mistakes
She must had forgotten.→ She must have forgotten.He can’t saw us.→ He can’t have seen us.
Key takeaway
Remember
Use modal perfect forms to make deductions about what probably, possibly or certainly did not happen.
Self-check
Quick check
- Identify the time relationship or intended meaning.
- Check the auxiliary, participle and clause pattern.
- Eliminate answers that fit the words but not the context.
Put it into practice
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