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