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 couldn't keep you couldn't keep he couldn't keep we couldn't keep you couldn't keep they couldn't keep
V-ing form
I couldn't be keeping you couldn't be keeping he couldn't be keeping we couldn't be keeping you couldn't be keeping they couldn't be keeping
Perfect
I couldn't have kept you couldn't have kept he couldn't have kept we couldn't have kept you couldn't have kept they couldn't have kept
V-ing perfect
I couldn't have been keeping you couldn't have been keeping he couldn't have been keeping we couldn't have been keeping you couldn't have been keeping they couldn't 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
couldn't I keep? couldn't you keep? couldn't he keep? couldn't we keep? couldn't you keep? couldn't they keep?
V-ing form
couldn't I be keeping? couldn't you be keeping? couldn't he be keeping? couldn't we be keeping? couldn't you be keeping? couldn't they be keeping?
Perfect
couldn't I have kept? couldn't you have kept? couldn't he have kept? couldn't we have kept? couldn't you have kept? couldn't they have kept?
V-ing perfect
couldn't I have been keeping? couldn't you have been keeping? couldn't he have been keeping? couldn't we have been keeping? couldn't you have been keeping? couldn't they have been keeping?