I could congest you could congest he could congest we could congest you could congest they could congest
V-ing form
I could be congesting you could be congesting he could be congesting we could be congesting you could be congesting they could be congesting
Perfect
I could have congested you could have congested he could have congested we could have congested you could have congested they could have congested
V-ing perfect
I could have been congesting you could have been congesting he could have been congesting we could have been congesting you could have been congesting they could have been congesting
Negation
Simple form
I could not congest you could not congest he could not congest we could not congest you could not congest they could not congest
V-ing form
I could not be congesting you could not be congesting he could not be congesting we could not be congesting you could not be congesting they could not be congesting
Perfect
I could not have congested you could not have congested he could not have congested we could not have congested you could not have congested they could not have congested
V-ing perfect
I could not have been congesting you could not have been congesting he could not have been congesting we could not have been congesting you could not have been congesting they could not have been congesting
Interrogative form
Simple form
could I congest? could you congest? could he congest? could we congest? could you congest? could they congest?
V-ing form
could I be congesting? could you be congesting? could he be congesting? could we be congesting? could you be congesting? could they be congesting?
Perfect
could I have congested? could you have congested? could he have congested? could we have congested? could you have congested? could they have congested?
V-ing perfect
could I have been congesting? could you have been congesting? could he have been congesting? could we have been congesting? could you have been congesting? could they have been congesting?
Interro-negative form
Simple form
could I not congest? could you not congest? could he not congest? could we not congest? could you not congest? could they not congest?
V-ing form
could I not be congesting? could you not be congesting? could he not be congesting? could we not be congesting? could you not be congesting? could they not be congesting?
Perfect
could I not have congested? could you not have congested? could he not have congested? could we not have congested? could you not have congested? could they not have congested?
V-ing perfect
could I not have been congesting? could you not have been congesting? could he not have been congesting? could we not have been congesting? could you not have been congesting? could they not have been congesting?