MODAL VERBS

1. Must + have+ past participle

1.1. Positive deduction about the past.

2. Can´t/Couldn´t+ have+ past participle

2.1. Negative deduction obout the past.

3. Should/Ought to+ have+ past participle

3.1. To express regret or criticisn about an action or somebody´s behaviour in the past.

4. May/might+ have+ past participle

4.1. Perhaps something happened but we are not sure

5. Could+havee+past participle

5.1. To express unfufilled possibility

6. needn´t+ have+ past participle

6.1. Something was not necessary but it was done.