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