I could comment you could comment he could comment we could comment you could comment they could comment
V-ing form
I could be commenting you could be commenting he could be commenting we could be commenting you could be commenting they could be commenting
Perfect
I could have commented you could have commented he could have commented we could have commented you could have commented they could have commented
V-ing perfect
I could have been commenting you could have been commenting he could have been commenting we could have been commenting you could have been commenting they could have been commenting
Negation
Simple form
I could not comment you could not comment he could not comment we could not comment you could not comment they could not comment
V-ing form
I could not be commenting you could not be commenting he could not be commenting we could not be commenting you could not be commenting they could not be commenting
Perfect
I could not have commented you could not have commented he could not have commented we could not have commented you could not have commented they could not have commented
V-ing perfect
I could not have been commenting you could not have been commenting he could not have been commenting we could not have been commenting you could not have been commenting they could not have been commenting
Interrogative form
Simple form
could I comment? could you comment? could he comment? could we comment? could you comment? could they comment?
V-ing form
could I be commenting? could you be commenting? could he be commenting? could we be commenting? could you be commenting? could they be commenting?
Perfect
could I have commented? could you have commented? could he have commented? could we have commented? could you have commented? could they have commented?
V-ing perfect
could I have been commenting? could you have been commenting? could he have been commenting? could we have been commenting? could you have been commenting? could they have been commenting?
Interro-negative form
Simple form
could I not comment? could you not comment? could he not comment? could we not comment? could you not comment? could they not comment?
V-ing form
could I not be commenting? could you not be commenting? could he not be commenting? could we not be commenting? could you not be commenting? could they not be commenting?
Perfect
could I not have commented? could you not have commented? could he not have commented? could we not have commented? could you not have commented? could they not have commented?
V-ing perfect
could I not have been commenting? could you not have been commenting? could he not have been commenting? could we not have been commenting? could you not have been commenting? could they not have been commenting?