Question

2.When do we use 'can' and 'could
in a sentence.​

Answer 1

Answer:

Can, like could and would, is used to ask a polite question, but can is only used to ask permission to do or say something ("Can I borrow your car?" "Can I get you something to drink?"). Could is the past tense of can, but it also has uses apart from that--and that is where the confusion lies.

Answer 2

We use 'can' for asking a permission.

Eg: "Can I borrow your book?"

'Could' is the past tense of 'can'.