I could call you could call he could call we could call you could call they could call
V-ing form
I could be calling you could be calling he could be calling we could be calling you could be calling they could be calling
Perfect
I could have called you could have called he 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 he 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 he 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 he 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 he 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 he 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 he call? could we call? could you call? could they call?
V-ing form
could I be calling? could you be calling? could he be calling? could we be calling? could you be calling? could they be calling?
Perfect
could I have called? could you have called? could he 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 he 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 he 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 he 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 he 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 he not have been calling? could we not have been calling? could you not have been calling? could they not have been calling?