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