Unit II Grammar

Modals degrees of certainty

Modals degrees of certainty can be used for expresing how sure you are about something. Degrees of certain can express differents tenses, past, present and future.

Must have +past participle: we use ir to make deductions about something that has happened, we feel quite sure about it.

Should have+past participle: use it to express the idea that something was needed but didn't Take place.
Might/May/Could have +past participle: use them to say that something was possible  in  the past but we are no sure.