I could talk you could talk he could talk we could talk you could talk they could talk
V-ing form
I could be talking you could be talking he could be talking we could be talking you could be talking they could be talking
Perfect
I could have talked you could have talked he could have talked we could have talked you could have talked they could have talked
V-ing perfect
I could have been talking you could have been talking he could have been talking we could have been talking you could have been talking they could have been talking
Negation
Simple form
I couldn't talk you couldn't talk he couldn't talk we couldn't talk you couldn't talk they couldn't talk
V-ing form
I couldn't be talking you couldn't be talking he couldn't be talking we couldn't be talking you couldn't be talking they couldn't be talking
Perfect
I couldn't have talked you couldn't have talked he couldn't have talked we couldn't have talked you couldn't have talked they couldn't have talked
V-ing perfect
I couldn't have been talking you couldn't have been talking he couldn't have been talking we couldn't have been talking you couldn't have been talking they couldn't have been talking
Interrogative form
Simple form
could I talk? could you talk? could he talk? could we talk? could you talk? could they talk?
V-ing form
could I be talking? could you be talking? could he be talking? could we be talking? could you be talking? could they be talking?
Perfect
could I have talked? could you have talked? could he have talked? could we have talked? could you have talked? could they have talked?
V-ing perfect
could I have been talking? could you have been talking? could he have been talking? could we have been talking? could you have been talking? could they have been talking?
Interro-negative form
Simple form
couldn't I talk? couldn't you talk? couldn't he talk? couldn't we talk? couldn't you talk? couldn't they talk?
V-ing form
couldn't I be talking? couldn't you be talking? couldn't he be talking? couldn't we be talking? couldn't you be talking? couldn't they be talking?
Perfect
couldn't I have talked? couldn't you have talked? couldn't he have talked? couldn't we have talked? couldn't you have talked? couldn't they have talked?
V-ing perfect
couldn't I have been talking? couldn't you have been talking? couldn't he have been talking? couldn't we have been talking? couldn't you have been talking? couldn't they have been talking?