Вивчаючи статистику

Could/May/Might + present infinitive: Possibility in a specific situation.
He should keep that souvenir - it may be valuable one day.
Note: we can use can/could/might in questions
BUT NOT may. Do you think that he can/could/might fix it?
Could/Might/Would + perfect infinitive: Refers to sth in the past that was possible but didn't happen. He might have succeeded if he had tried harder.
Ability/Inability
We use the following verbs to talk about ability:

Present	can, can't, be able to, manage to	I can't swim.
Past	could, couldn't, he able to, manage to	They weren't able to find out his name.
Perfect	be able to, manage to	Have you managed to finish the report yet?
Future	be able to, manage to	I won't be able to meet you later.

Can expresses ability in the present/future.I can lean play the piano.
Could expresses general, repeated ability in the past. I could talk when I was two.
Was(n't) able to expresses (in)ability on a specific occasion in the past. I was(n't) able to get to the airport in time to catch my flight.
Couldn't may be used to express any kind of inability in the past, repeated or specific. I couldn't speak French when I was two. I couldn't/wasn't able to remember his name when I saw him in the street.
Logical Assumptions/Deductions
Must, may, can't, etc + bare infinitive: for assumptions about the present.
perfect infinitive: for assumptions about the past.
Must = almost certain that this is/was true. (= very likely)
She's been working all day, so she must be really tired!
She was working all day yesterday, so she must have been really tired!
May/Might/Could = possible that this is/was true. (= possible)
John isn't at work today - he may/might be out of town on business.
John wasn't at work yesterday - he may/might have been out of town on business.
Can't/couldn't = almost certain that this is/was impossible.(=very unlikely)
That can't be Janet over there - she's at her grandparents’ at the moment.
That can't have been Janet you saw - she was at her grandparents' at that time.
Could, may and might express the same degree of possibility:
He may/might/could remember some things already.