I could comment you could comment she could comment we could comment you could comment they could comment
V-ing form
I could be commenting you could be commenting she could be commenting we could be commenting you could be commenting they could be commenting
Perfect
I could have commented you could have commented she 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 she 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 she 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 she 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 she 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 she 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 she comment? could we comment? could you comment? could they comment?
V-ing form
could I be commenting? could you be commenting? could she be commenting? could we be commenting? could you be commenting? could they be commenting?
Perfect
could I have commented? could you have commented? could she 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 she 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 she 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 she 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 she 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 she not have been commenting? could we not have been commenting? could you not have been commenting? could they not have been commenting?