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 couldn't gab you couldn't gab he couldn't gab we couldn't gab you couldn't gab they couldn't gab
V-ing form
I couldn't be gabbing you couldn't be gabbing he couldn't be gabbing we couldn't be gabbing you couldn't be gabbing they couldn't be gabbing
Perfect
I couldn't have gabbed you couldn't have gabbed he couldn't have gabbed we couldn't have gabbed you couldn't have gabbed they couldn't have gabbed
V-ing perfect
I couldn't have been gabbing you couldn't have been gabbing he couldn't have been gabbing we couldn't have been gabbing you couldn't have been gabbing they couldn't 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
couldn't I gab? couldn't you gab? couldn't he gab? couldn't we gab? couldn't you gab? couldn't they gab?
V-ing form
couldn't I be gabbing? couldn't you be gabbing? couldn't he be gabbing? couldn't we be gabbing? couldn't you be gabbing? couldn't they be gabbing?
Perfect
couldn't I have gabbed? couldn't you have gabbed? couldn't he have gabbed? couldn't we have gabbed? couldn't you have gabbed? couldn't they have gabbed?
V-ing perfect
couldn't I have been gabbing? couldn't you have been gabbing? couldn't he have been gabbing? couldn't we have been gabbing? couldn't you have been gabbing? couldn't they have been gabbing?