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