I could answer you could answer she could answer we could answer you could answer they could answer
V-ing form
I could be answering you could be answering she could be answering we could be answering you could be answering they could be answering
Perfect
I could have answered you could have answered she could have answered we could have answered you could have answered they could have answered
V-ing perfect
I could have been answering you could have been answering she could have been answering we could have been answering you could have been answering they could have been answering
Negation
Simple form
I could not answer you could not answer she could not answer we could not answer you could not answer they could not answer
V-ing form
I could not be answering you could not be answering she could not be answering we could not be answering you could not be answering they could not be answering
Perfect
I could not have answered you could not have answered she could not have answered we could not have answered you could not have answered they could not have answered
V-ing perfect
I could not have been answering you could not have been answering she could not have been answering we could not have been answering you could not have been answering they could not have been answering
Interrogative form
Simple form
could I answer? could you answer? could she answer? could we answer? could you answer? could they answer?
V-ing form
could I be answering? could you be answering? could she be answering? could we be answering? could you be answering? could they be answering?
Perfect
could I have answered? could you have answered? could she have answered? could we have answered? could you have answered? could they have answered?
V-ing perfect
could I have been answering? could you have been answering? could she have been answering? could we have been answering? could you have been answering? could they have been answering?
Interro-negative form
Simple form
could I not answer? could you not answer? could she not answer? could we not answer? could you not answer? could they not answer?
V-ing form
could I not be answering? could you not be answering? could she not be answering? could we not be answering? could you not be answering? could they not be answering?
Perfect
could I not have answered? could you not have answered? could she not have answered? could we not have answered? could you not have answered? could they not have answered?
V-ing perfect
could I not have been answering? could you not have been answering? could she not have been answering? could we not have been answering? could you not have been answering? could they not have been answering?