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 couldn't discuss you couldn't discuss she couldn't discuss we couldn't discuss you couldn't discuss they couldn't discuss
V-ing form
I couldn't be discussing you couldn't be discussing she couldn't be discussing we couldn't be discussing you couldn't be discussing they couldn't be discussing
Perfect
I couldn't have discussed you couldn't have discussed she couldn't have discussed we couldn't have discussed you couldn't have discussed they couldn't have discussed
V-ing perfect
I couldn't have been discussing you couldn't have been discussing she couldn't have been discussing we couldn't have been discussing you couldn't have been discussing they couldn't 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
couldn't I discuss? couldn't you discuss? couldn't she discuss? couldn't we discuss? couldn't you discuss? couldn't they discuss?
V-ing form
couldn't I be discussing? couldn't you be discussing? couldn't she be discussing? couldn't we be discussing? couldn't you be discussing? couldn't they be discussing?
Perfect
couldn't I have discussed? couldn't you have discussed? couldn't she have discussed? couldn't we have discussed? couldn't you have discussed? couldn't they have discussed?
V-ing perfect
couldn't I have been discussing? couldn't you have been discussing? couldn't she have been discussing? couldn't we have been discussing? couldn't you have been discussing? couldn't they have been discussing?