2/ Inferential meaning.

1. Doubt, surprise:

• about the present

	do
CAN/COULD Smb.	be doing	smth.?
	be done

e.g. Can she be writing a test now?(Неужели она сейчас пишет контрольную?)

• about the past

	have done
CAN/COULD Smb.	have been doing	smth.?
	have been done

e.g. Can she have been playing football so long?

2. A very strong doubt, impossibility, improbability:

• about the present

	can’t	do
Smb.		be doing	smth. (it is not possible)
	couldn’t	be done

e.g. She can’t be writing a test now. (не может быть, чтобы он сейчас писала контрольную)

• about the past

	can’t	have done
Smb.		have been doing	smth. (it is not possible)
	couldn’t	have been done

e.g. She couldn’t have finished it. (Не может быть, чтобы она закончила)

3. Uncertainty (no negative form)

• about the present

	can	do
Smb.		be doing	smth. (it is not possible)
	could	be done

e.g. He could be at home (Возможно, он дома)

• about the past

	can	have done
Smb.		have been doing	smth. (it is not possible)
	could	have been done

e.g. He could have gone to the cinema.

3/ Imperative usage

1. Permission.

	can
Smb.		do	smth.
	could

e.g. You can go.

2. Asking for permission.

Can
	I	do	smth?
Could

e.g. Can I go?

3. Request, asking for help.

Can
	you	do	smth?
Could

e.g. Can you help me?

4. Prohibition.

You	can’t	do	smth.

e.g. You can’t cross the street here.

5. Suggestions, orders.

You
	can/could	do	smth.
We

e.g. We could go to the theatre.

You can open the door.

6. Offers.

Can I …?

What can I …?

e.g. Can I help you?

What can I do for you?

7. Irritation, annoyance, reproach.

You		do
	(might)/could		smth.
We		have done