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