I could graft you could graft he could graft we could graft you could graft they could graft
V-ing form
I could be grafting you could be grafting he could be grafting we could be grafting you could be grafting they could be grafting
Perfect
I could have grafted you could have grafted he could have grafted we could have grafted you could have grafted they could have grafted
V-ing perfect
I could have been grafting you could have been grafting he could have been grafting we could have been grafting you could have been grafting they could have been grafting
Negation
Simple form
I could not graft you could not graft he could not graft we could not graft you could not graft they could not graft
V-ing form
I could not be grafting you could not be grafting he could not be grafting we could not be grafting you could not be grafting they could not be grafting
Perfect
I could not have grafted you could not have grafted he could not have grafted we could not have grafted you could not have grafted they could not have grafted
V-ing perfect
I could not have been grafting you could not have been grafting he could not have been grafting we could not have been grafting you could not have been grafting they could not have been grafting
Interrogative form
Simple form
could I graft? could you graft? could he graft? could we graft? could you graft? could they graft?
V-ing form
could I be grafting? could you be grafting? could he be grafting? could we be grafting? could you be grafting? could they be grafting?
Perfect
could I have grafted? could you have grafted? could he have grafted? could we have grafted? could you have grafted? could they have grafted?
V-ing perfect
could I have been grafting? could you have been grafting? could he have been grafting? could we have been grafting? could you have been grafting? could they have been grafting?
Interro-negative form
Simple form
could I not graft? could you not graft? could he not graft? could we not graft? could you not graft? could they not graft?
V-ing form
could I not be grafting? could you not be grafting? could he not be grafting? could we not be grafting? could you not be grafting? could they not be grafting?
Perfect
could I not have grafted? could you not have grafted? could he not have grafted? could we not have grafted? could you not have grafted? could they not have grafted?
V-ing perfect
could I not have been grafting? could you not have been grafting? could he not have been grafting? could we not have been grafting? could you not have been grafting? could they not have been grafting?