I could keen you could keen he could keen we could keen you could keen they could keen
V-ing form
I could be keening you could be keening he could be keening we could be keening you could be keening they could be keening
Perfect
I could have keened you could have keened he 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 he could have been keening we could have been keening you could have been keening they could have been keening
Negation
Simple form
I couldn't keen you couldn't keen he couldn't keen we couldn't keen you couldn't keen they couldn't keen
V-ing form
I couldn't be keening you couldn't be keening he couldn't be keening we couldn't be keening you couldn't be keening they couldn't be keening
Perfect
I couldn't have keened you couldn't have keened he couldn't have keened we couldn't have keened you couldn't have keened they couldn't have keened
V-ing perfect
I couldn't have been keening you couldn't have been keening he couldn't have been keening we couldn't have been keening you couldn't have been keening they couldn't have been keening
Interrogative form
Simple form
could I keen? could you keen? could he keen? could we keen? could you keen? could they keen?
V-ing form
could I be keening? could you be keening? could he be keening? could we be keening? could you be keening? could they be keening?
Perfect
could I have keened? could you have keened? could he 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 he have been keening? could we have been keening? could you have been keening? could they have been keening?
Interro-negative form
Simple form
couldn't I keen? couldn't you keen? couldn't he keen? couldn't we keen? couldn't you keen? couldn't they keen?
V-ing form
couldn't I be keening? couldn't you be keening? couldn't he be keening? couldn't we be keening? couldn't you be keening? couldn't they be keening?
Perfect
couldn't I have keened? couldn't you have keened? couldn't he have keened? couldn't we have keened? couldn't you have keened? couldn't they have keened?
V-ing perfect
couldn't I have been keening? couldn't you have been keening? couldn't he have been keening? couldn't we have been keening? couldn't you have been keening? couldn't they have been keening?