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