I could call you could call she could call we could call you could call they could call
V-ing form
I could be calling you could be calling she could be calling we could be calling you could be calling they could be calling
Perfect
I could have called you could have called she could have called we could have called you could have called they could have called
V-ing perfect
I could have been calling you could have been calling she could have been calling we could have been calling you could have been calling they could have been calling
Negation
Simple form
I could not call you could not call she could not call we could not call you could not call they could not call
V-ing form
I could not be calling you could not be calling she could not be calling we could not be calling you could not be calling they could not be calling
Perfect
I could not have called you could not have called she could not have called we could not have called you could not have called they could not have called
V-ing perfect
I could not have been calling you could not have been calling she could not have been calling we could not have been calling you could not have been calling they could not have been calling
Interrogative form
Simple form
could I call? could you call? could she call? could we call? could you call? could they call?
V-ing form
could I be calling? could you be calling? could she be calling? could we be calling? could you be calling? could they be calling?
Perfect
could I have called? could you have called? could she have called? could we have called? could you have called? could they have called?
V-ing perfect
could I have been calling? could you have been calling? could she have been calling? could we have been calling? could you have been calling? could they have been calling?
Interro-negative form
Simple form
could I not call? could you not call? could she not call? could we not call? could you not call? could they not call?
V-ing form
could I not be calling? could you not be calling? could she not be calling? could we not be calling? could you not be calling? could they not be calling?
Perfect
could I not have called? could you not have called? could she not have called? could we not have called? could you not have called? could they not have called?
V-ing perfect
could I not have been calling? could you not have been calling? could she not have been calling? could we not have been calling? could you not have been calling? could they not have been calling?