| All the modal verbs given above can be used with the perfect infinitive to express varying degrees of certainty about the past.Again,will/would is the most certain and might/could is the least certain. |
1.You say you stayed in a hotel near the lake?That would have been my parents' hotel.
2.It won't have been Peter you met at the party last night.He was ill in bed.
It must have been Simon.He looks very like Peter.
3.It can't have been a very interesting party.
4.Where's Henry? He should have been here ages ago!
5.He may have got lost.