I could brush you could brush she could brush we could brush you could brush they could brush
V-ing form
I could be brushing you could be brushing she could be brushing we could be brushing you could be brushing they could be brushing
Perfect
I could have brushed you could have brushed she 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 she 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 she 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 she 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 she 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 she 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 she brush? could we brush? could you brush? could they brush?
V-ing form
could I be brushing? could you be brushing? could she be brushing? could we be brushing? could you be brushing? could they be brushing?
Perfect
could I have brushed? could you have brushed? could she 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 she 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 she 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 she 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 she 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 she have been brushing? couldn't we have been brushing? couldn't you have been brushing? couldn't they have been brushing?