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