I could keep you could keep he could keep we could keep you could keep they could keep
V-ing form
I could be keeping you could be keeping he could be keeping we could be keeping you could be keeping they could be keeping
Perfect
I could have kept you could have kept he could have kept we could have kept you could have kept they could have kept
V-ing perfect
I could have been keeping you could have been keeping he could have been keeping we could have been keeping you could have been keeping they could have been keeping
Negation
Simple form
I could not keep you could not keep he could not keep we could not keep you could not keep they could not keep
V-ing form
I could not be keeping you could not be keeping he could not be keeping we could not be keeping you could not be keeping they could not be keeping
Perfect
I could not have kept you could not have kept he could not have kept we could not have kept you could not have kept they could not have kept
V-ing perfect
I could not have been keeping you could not have been keeping he could not have been keeping we could not have been keeping you could not have been keeping they could not have been keeping
Interrogative form
Simple form
could I keep? could you keep? could he keep? could we keep? could you keep? could they keep?
V-ing form
could I be keeping? could you be keeping? could he be keeping? could we be keeping? could you be keeping? could they be keeping?
Perfect
could I have kept? could you have kept? could he have kept? could we have kept? could you have kept? could they have kept?
V-ing perfect
could I have been keeping? could you have been keeping? could he have been keeping? could we have been keeping? could you have been keeping? could they have been keeping?
Interro-negative form
Simple form
could I not keep? could you not keep? could he not keep? could we not keep? could you not keep? could they not keep?
V-ing form
could I not be keeping? could you not be keeping? could he not be keeping? could we not be keeping? could you not be keeping? could they not be keeping?
Perfect
could I not have kept? could you not have kept? could he not have kept? could we not have kept? could you not have kept? could they not have kept?
V-ing perfect
could I not have been keeping? could you not have been keeping? could he not have been keeping? could we not have been keeping? could you not have been keeping? could they not have been keeping?