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 couldn't graft you couldn't graft he couldn't graft we couldn't graft you couldn't graft they couldn't graft
V-ing form
I couldn't be grafting you couldn't be grafting he couldn't be grafting we couldn't be grafting you couldn't be grafting they couldn't be grafting
Perfect
I couldn't have grafted you couldn't have grafted he couldn't have grafted we couldn't have grafted you couldn't have grafted they couldn't have grafted
V-ing perfect
I couldn't have been grafting you couldn't have been grafting he couldn't have been grafting we couldn't have been grafting you couldn't have been grafting they couldn't 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
couldn't I graft? couldn't you graft? couldn't he graft? couldn't we graft? couldn't you graft? couldn't they graft?
V-ing form
couldn't I be grafting? couldn't you be grafting? couldn't he be grafting? couldn't we be grafting? couldn't you be grafting? couldn't they be grafting?
Perfect
couldn't I have grafted? couldn't you have grafted? couldn't he have grafted? couldn't we have grafted? couldn't you have grafted? couldn't they have grafted?
V-ing perfect
couldn't I have been grafting? couldn't you have been grafting? couldn't he have been grafting? couldn't we have been grafting? couldn't you have been grafting? couldn't they have been grafting?