I could discuss you could discuss she could discuss we could discuss you could discuss they could discuss
V-ing form
I could be discussing you could be discussing she could be discussing we could be discussing you could be discussing they could be discussing
Perfect
I could have discussed you could have discussed she could have discussed we could have discussed you could have discussed they could have discussed
V-ing perfect
I could have been discussing you could have been discussing she could have been discussing we could have been discussing you could have been discussing they could have been discussing
Negation
Simple form
I could not discuss you could not discuss she could not discuss we could not discuss you could not discuss they could not discuss
V-ing form
I could not be discussing you could not be discussing she could not be discussing we could not be discussing you could not be discussing they could not be discussing
Perfect
I could not have discussed you could not have discussed she could not have discussed we could not have discussed you could not have discussed they could not have discussed
V-ing perfect
I could not have been discussing you could not have been discussing she could not have been discussing we could not have been discussing you could not have been discussing they could not have been discussing
Interrogative form
Simple form
could I discuss? could you discuss? could she discuss? could we discuss? could you discuss? could they discuss?
V-ing form
could I be discussing? could you be discussing? could she be discussing? could we be discussing? could you be discussing? could they be discussing?
Perfect
could I have discussed? could you have discussed? could she have discussed? could we have discussed? could you have discussed? could they have discussed?
V-ing perfect
could I have been discussing? could you have been discussing? could she have been discussing? could we have been discussing? could you have been discussing? could they have been discussing?
Interro-negative form
Simple form
could I not discuss? could you not discuss? could she not discuss? could we not discuss? could you not discuss? could they not discuss?
V-ing form
could I not be discussing? could you not be discussing? could she not be discussing? could we not be discussing? could you not be discussing? could they not be discussing?
Perfect
could I not have discussed? could you not have discussed? could she not have discussed? could we not have discussed? could you not have discussed? could they not have discussed?
V-ing perfect
could I not have been discussing? could you not have been discussing? could she not have been discussing? could we not have been discussing? could you not have been discussing? could they not have been discussing?