I could supplement you could supplement he could supplement we could supplement you could supplement they could supplement
V-ing form
I could be supplementing you could be supplementing he could be supplementing we could be supplementing you could be supplementing they could be supplementing
Perfect
I could have supplemented you could have supplemented he could have supplemented we could have supplemented you could have supplemented they could have supplemented
V-ing perfect
I could have been supplementing you could have been supplementing he could have been supplementing we could have been supplementing you could have been supplementing they could have been supplementing
Negation
Simple form
I could not supplement you could not supplement he could not supplement we could not supplement you could not supplement they could not supplement
V-ing form
I could not be supplementing you could not be supplementing he could not be supplementing we could not be supplementing you could not be supplementing they could not be supplementing
Perfect
I could not have supplemented you could not have supplemented he could not have supplemented we could not have supplemented you could not have supplemented they could not have supplemented
V-ing perfect
I could not have been supplementing you could not have been supplementing he could not have been supplementing we could not have been supplementing you could not have been supplementing they could not have been supplementing
Interrogative form
Simple form
could I supplement? could you supplement? could he supplement? could we supplement? could you supplement? could they supplement?
V-ing form
could I be supplementing? could you be supplementing? could he be supplementing? could we be supplementing? could you be supplementing? could they be supplementing?
Perfect
could I have supplemented? could you have supplemented? could he have supplemented? could we have supplemented? could you have supplemented? could they have supplemented?
V-ing perfect
could I have been supplementing? could you have been supplementing? could he have been supplementing? could we have been supplementing? could you have been supplementing? could they have been supplementing?
Interro-negative form
Simple form
could I not supplement? could you not supplement? could he not supplement? could we not supplement? could you not supplement? could they not supplement?
V-ing form
could I not be supplementing? could you not be supplementing? could he not be supplementing? could we not be supplementing? could you not be supplementing? could they not be supplementing?
Perfect
could I not have supplemented? could you not have supplemented? could he not have supplemented? could we not have supplemented? could you not have supplemented? could they not have supplemented?
V-ing perfect
could I not have been supplementing? could you not have been supplementing? could he not have been supplementing? could we not have been supplementing? could you not have been supplementing? could they not have been supplementing?