I could talk you could talk she could talk we could talk you could talk they could talk
V-ing form
I could be talking you could be talking she could be talking we could be talking you could be talking they could be talking
Perfect
I could have talked you could have talked she 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 she could have been talking we could have been talking you could have been talking they could have been talking
Negation
Simple form
I could not talk you could not talk she could not talk we could not talk you could not talk they could not talk
V-ing form
I could not be talking you could not be talking she could not be talking we could not be talking you could not be talking they could not be talking
Perfect
I could not have talked you could not have talked she could not have talked we could not have talked you could not have talked they could not have talked
V-ing perfect
I could not have been talking you could not have been talking she could not have been talking we could not have been talking you could not have been talking they could not have been talking
Interrogative form
Simple form
could I talk? could you talk? could she talk? could we talk? could you talk? could they talk?
V-ing form
could I be talking? could you be talking? could she be talking? could we be talking? could you be talking? could they be talking?
Perfect
could I have talked? could you have talked? could she 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 she have been talking? could we have been talking? could you have been talking? could they have been talking?
Interro-negative form
Simple form
could I not talk? could you not talk? could she not talk? could we not talk? could you not talk? could they not talk?
V-ing form
could I not be talking? could you not be talking? could she not be talking? could we not be talking? could you not be talking? could they not be talking?
Perfect
could I not have talked? could you not have talked? could she not have talked? could we not have talked? could you not have talked? could they not have talked?
V-ing perfect
could I not have been talking? could you not have been talking? could she not have been talking? could we not have been talking? could you not have been talking? could they not have been talking?