I could state you could state he could state we could state you could state they could state
V-ing form
I could be stating you could be stating he could be stating we could be stating you could be stating they could be stating
Perfect
I could have stated you could have stated he could have stated we could have stated you could have stated they could have stated
V-ing perfect
I could have been stating you could have been stating he could have been stating we could have been stating you could have been stating they could have been stating
Negation
Simple form
I couldn't state you couldn't state he couldn't state we couldn't state you couldn't state they couldn't state
V-ing form
I couldn't be stating you couldn't be stating he couldn't be stating we couldn't be stating you couldn't be stating they couldn't be stating
Perfect
I couldn't have stated you couldn't have stated he couldn't have stated we couldn't have stated you couldn't have stated they couldn't have stated
V-ing perfect
I couldn't have been stating you couldn't have been stating he couldn't have been stating we couldn't have been stating you couldn't have been stating they couldn't have been stating
Interrogative form
Simple form
could I state? could you state? could he state? could we state? could you state? could they state?
V-ing form
could I be stating? could you be stating? could he be stating? could we be stating? could you be stating? could they be stating?
Perfect
could I have stated? could you have stated? could he have stated? could we have stated? could you have stated? could they have stated?
V-ing perfect
could I have been stating? could you have been stating? could he have been stating? could we have been stating? could you have been stating? could they have been stating?
Interro-negative form
Simple form
couldn't I state? couldn't you state? couldn't he state? couldn't we state? couldn't you state? couldn't they state?
V-ing form
couldn't I be stating? couldn't you be stating? couldn't he be stating? couldn't we be stating? couldn't you be stating? couldn't they be stating?
Perfect
couldn't I have stated? couldn't you have stated? couldn't he have stated? couldn't we have stated? couldn't you have stated? couldn't they have stated?
V-ing perfect
couldn't I have been stating? couldn't you have been stating? couldn't he have been stating? couldn't we have been stating? couldn't you have been stating? couldn't they have been stating?