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