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 could not bum you could not bum he could not bum we could not bum you could not bum they could not bum
V-ing form
I could not be bumming you could not be bumming he could not be bumming we could not be bumming you could not be bumming they could not be bumming
Perfect
I could not have bummed you could not have bummed he could not have bummed we could not have bummed you could not have bummed they could not have bummed
V-ing perfect
I could not have been bumming you could not have been bumming he could not have been bumming we could not have been bumming you could not have been bumming they could not 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
could I not bum? could you not bum? could he not bum? could we not bum? could you not bum? could they not bum?
V-ing form
could I not be bumming? could you not be bumming? could he not be bumming? could we not be bumming? could you not be bumming? could they not be bumming?
Perfect
could I not have bummed? could you not have bummed? could he not have bummed? could we not have bummed? could you not have bummed? could they not have bummed?
V-ing perfect
could I not have been bumming? could you not have been bumming? could he not have been bumming? could we not have been bumming? could you not have been bumming? could they not have been bumming?