I could gab you could gab he could gab we could gab you could gab they could gab
V-ing form
I could be gabbing you could be gabbing he could be gabbing we could be gabbing you could be gabbing they could be gabbing
Perfect
I could have gabbed you could have gabbed he could have gabbed we could have gabbed you could have gabbed they could have gabbed
V-ing perfect
I could have been gabbing you could have been gabbing he could have been gabbing we could have been gabbing you could have been gabbing they could have been gabbing
Negation
Simple form
I could not gab you could not gab he could not gab we could not gab you could not gab they could not gab
V-ing form
I could not be gabbing you could not be gabbing he could not be gabbing we could not be gabbing you could not be gabbing they could not be gabbing
Perfect
I could not have gabbed you could not have gabbed he could not have gabbed we could not have gabbed you could not have gabbed they could not have gabbed
V-ing perfect
I could not have been gabbing you could not have been gabbing he could not have been gabbing we could not have been gabbing you could not have been gabbing they could not have been gabbing
Interrogative form
Simple form
could I gab? could you gab? could he gab? could we gab? could you gab? could they gab?
V-ing form
could I be gabbing? could you be gabbing? could he be gabbing? could we be gabbing? could you be gabbing? could they be gabbing?
Perfect
could I have gabbed? could you have gabbed? could he have gabbed? could we have gabbed? could you have gabbed? could they have gabbed?
V-ing perfect
could I have been gabbing? could you have been gabbing? could he have been gabbing? could we have been gabbing? could you have been gabbing? could they have been gabbing?
Interro-negative form
Simple form
could I not gab? could you not gab? could he not gab? could we not gab? could you not gab? could they not gab?
V-ing form
could I not be gabbing? could you not be gabbing? could he not be gabbing? could we not be gabbing? could you not be gabbing? could they not be gabbing?
Perfect
could I not have gabbed? could you not have gabbed? could he not have gabbed? could we not have gabbed? could you not have gabbed? could they not have gabbed?
V-ing perfect
could I not have been gabbing? could you not have been gabbing? could he not have been gabbing? could we not have been gabbing? could you not have been gabbing? could they not have been gabbing?