I could keen you could keen she could keen we could keen you could keen they could keen
V-ing form
I could be keening you could be keening she could be keening we could be keening you could be keening they could be keening
Perfect
I could have keened you could have keened she could have keened we could have keened you could have keened they could have keened
V-ing perfect
I could have been keening you could have been keening she could have been keening we could have been keening you could have been keening they could have been keening
Negation
Simple form
I could not keen you could not keen she could not keen we could not keen you could not keen they could not keen
V-ing form
I could not be keening you could not be keening she could not be keening we could not be keening you could not be keening they could not be keening
Perfect
I could not have keened you could not have keened she could not have keened we could not have keened you could not have keened they could not have keened
V-ing perfect
I could not have been keening you could not have been keening she could not have been keening we could not have been keening you could not have been keening they could not have been keening
Interrogative form
Simple form
could I keen? could you keen? could she keen? could we keen? could you keen? could they keen?
V-ing form
could I be keening? could you be keening? could she be keening? could we be keening? could you be keening? could they be keening?
Perfect
could I have keened? could you have keened? could she have keened? could we have keened? could you have keened? could they have keened?
V-ing perfect
could I have been keening? could you have been keening? could she have been keening? could we have been keening? could you have been keening? could they have been keening?
Interro-negative form
Simple form
could I not keen? could you not keen? could she not keen? could we not keen? could you not keen? could they not keen?
V-ing form
could I not be keening? could you not be keening? could she not be keening? could we not be keening? could you not be keening? could they not be keening?
Perfect
could I not have keened? could you not have keened? could she not have keened? could we not have keened? could you not have keened? could they not have keened?
V-ing perfect
could I not have been keening? could you not have been keening? could she not have been keening? could we not have been keening? could you not have been keening? could they not have been keening?