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