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 couldn't comment you couldn't comment she couldn't comment we couldn't comment you couldn't comment they couldn't comment
V-ing form
I couldn't be commenting you couldn't be commenting she couldn't be commenting we couldn't be commenting you couldn't be commenting they couldn't be commenting
Perfect
I couldn't have commented you couldn't have commented she couldn't have commented we couldn't have commented you couldn't have commented they couldn't have commented
V-ing perfect
I couldn't have been commenting you couldn't have been commenting she couldn't have been commenting we couldn't have been commenting you couldn't have been commenting they couldn't 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
couldn't I comment? couldn't you comment? couldn't she comment? couldn't we comment? couldn't you comment? couldn't they comment?
V-ing form
couldn't I be commenting? couldn't you be commenting? couldn't she be commenting? couldn't we be commenting? couldn't you be commenting? couldn't they be commenting?
Perfect
couldn't I have commented? couldn't you have commented? couldn't she have commented? couldn't we have commented? couldn't you have commented? couldn't they have commented?
V-ing perfect
couldn't I have been commenting? couldn't you have been commenting? couldn't she have been commenting? couldn't we have been commenting? couldn't you have been commenting? couldn't they have been commenting?