modal + have + 3 forma lub ed

 1. Where is Mike ?

Maybe he forgot= He might have forgotten

2. Where is Susan? 

Probably she overslept= She might have overslept

3. I lost my money. I am sure I lost it at work=

 I must have lost it at work

4. You didn't see Mike. I am sure of it. He is in Canada. 

You can't have seen Mike. 

5.Probably  she didn't cheat.

She might not have cheated. 

6.  It is a pity you didn't visit me. 

You could have visited me. ( regret) 

7.  We have a lot of bread. It was not necessary of you to buy it. 

You needn't have bought it. 

8. You didn't clean your house. 

You should have cleaned your house. 

!!!

I had to work a lot.

I could swim when I was five.