I could agree you could agree he could agree we could agree you could agree they could agree
V-ing form
I could be agreeing you could be agreeing he could be agreeing we could be agreeing you could be agreeing they could be agreeing
Perfect
I could have agreed you could have agreed he could have agreed we could have agreed you could have agreed they could have agreed
V-ing perfect
I could have been agreeing you could have been agreeing he could have been agreeing we could have been agreeing you could have been agreeing they could have been agreeing
Negation
Simple form
I could not agree you could not agree he could not agree we could not agree you could not agree they could not agree
V-ing form
I could not be agreeing you could not be agreeing he could not be agreeing we could not be agreeing you could not be agreeing they could not be agreeing
Perfect
I could not have agreed you could not have agreed he could not have agreed we could not have agreed you could not have agreed they could not have agreed
V-ing perfect
I could not have been agreeing you could not have been agreeing he could not have been agreeing we could not have been agreeing you could not have been agreeing they could not have been agreeing
Interrogative form
Simple form
could I agree? could you agree? could he agree? could we agree? could you agree? could they agree?
V-ing form
could I be agreeing? could you be agreeing? could he be agreeing? could we be agreeing? could you be agreeing? could they be agreeing?
Perfect
could I have agreed? could you have agreed? could he have agreed? could we have agreed? could you have agreed? could they have agreed?
V-ing perfect
could I have been agreeing? could you have been agreeing? could he have been agreeing? could we have been agreeing? could you have been agreeing? could they have been agreeing?
Interro-negative form
Simple form
could I not agree? could you not agree? could he not agree? could we not agree? could you not agree? could they not agree?
V-ing form
could I not be agreeing? could you not be agreeing? could he not be agreeing? could we not be agreeing? could you not be agreeing? could they not be agreeing?
Perfect
could I not have agreed? could you not have agreed? could he not have agreed? could we not have agreed? could you not have agreed? could they not have agreed?
V-ing perfect
could I not have been agreeing? could you not have been agreeing? could he not have been agreeing? could we not have been agreeing? could you not have been agreeing? could they not have been agreeing?