I could know you could know she could know we could know you could know they could know
V-ing form
I could be knowing you could be knowing she could be knowing we could be knowing you could be knowing they could be knowing
Perfect
I could have known you could have known she could have known we could have known you could have known they could have known
V-ing perfect
I could have been knowing you could have been knowing she could have been knowing we could have been knowing you could have been knowing they could have been knowing
Negation
Simple form
I could not know you could not know she could not know we could not know you could not know they could not know
V-ing form
I could not be knowing you could not be knowing she could not be knowing we could not be knowing you could not be knowing they could not be knowing
Perfect
I could not have known you could not have known she could not have known we could not have known you could not have known they could not have known
V-ing perfect
I could not have been knowing you could not have been knowing she could not have been knowing we could not have been knowing you could not have been knowing they could not have been knowing
Interrogative form
Simple form
could I know? could you know? could she know? could we know? could you know? could they know?
V-ing form
could I be knowing? could you be knowing? could she be knowing? could we be knowing? could you be knowing? could they be knowing?
Perfect
could I have known? could you have known? could she have known? could we have known? could you have known? could they have known?
V-ing perfect
could I have been knowing? could you have been knowing? could she have been knowing? could we have been knowing? could you have been knowing? could they have been knowing?
Interro-negative form
Simple form
could I not know? could you not know? could she not know? could we not know? could you not know? could they not know?
V-ing form
could I not be knowing? could you not be knowing? could she not be knowing? could we not be knowing? could you not be knowing? could they not be knowing?
Perfect
could I not have known? could you not have known? could she not have known? could we not have known? could you not have known? could they not have known?
V-ing perfect
could I not have been knowing? could you not have been knowing? could she not have been knowing? could we not have been knowing? could you not have been knowing? could they not have been knowing?