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