I could litter you could litter she could litter we could litter you could litter they could litter
V-ing form
I could be littering you could be littering she could be littering we could be littering you could be littering they could be littering
Perfect
I could have littered you could have littered she 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 she could have been littering we could have been littering you could have been littering they could have been littering
Negation
Simple form
I could not litter you could not litter she could not litter we could not litter you could not litter they could not litter
V-ing form
I could not be littering you could not be littering she could not be littering we could not be littering you could not be littering they could not be littering
Perfect
I could not have littered you could not have littered she could not have littered we could not have littered you could not have littered they could not have littered
V-ing perfect
I could not have been littering you could not have been littering she could not have been littering we could not have been littering you could not have been littering they could not have been littering
Interrogative form
Simple form
could I litter? could you litter? could she litter? could we litter? could you litter? could they litter?
V-ing form
could I be littering? could you be littering? could she be littering? could we be littering? could you be littering? could they be littering?
Perfect
could I have littered? could you have littered? could she 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 she have been littering? could we have been littering? could you have been littering? could they have been littering?
Interro-negative form
Simple form
could I not litter? could you not litter? could she not litter? could we not litter? could you not litter? could they not litter?
V-ing form
could I not be littering? could you not be littering? could she not be littering? could we not be littering? could you not be littering? could they not be littering?
Perfect
could I not have littered? could you not have littered? could she not have littered? could we not have littered? could you not have littered? could they not have littered?
V-ing perfect
could I not have been littering? could you not have been littering? could she not have been littering? could we not have been littering? could you not have been littering? could they not have been littering?