I could add you could add she could add we could add you could add they could add
V-ing form
I could be adding you could be adding she could be adding we could be adding you could be adding they could be adding
Perfect
I could have added you could have added she could have added we could have added you could have added they could have added
V-ing perfect
I could have been adding you could have been adding she could have been adding we could have been adding you could have been adding they could have been adding
Negation
Simple form
I couldn't add you couldn't add she couldn't add we couldn't add you couldn't add they couldn't add
V-ing form
I couldn't be adding you couldn't be adding she couldn't be adding we couldn't be adding you couldn't be adding they couldn't be adding
Perfect
I couldn't have added you couldn't have added she couldn't have added we couldn't have added you couldn't have added they couldn't have added
V-ing perfect
I couldn't have been adding you couldn't have been adding she couldn't have been adding we couldn't have been adding you couldn't have been adding they couldn't have been adding
Interrogative form
Simple form
could I add? could you add? could she add? could we add? could you add? could they add?
V-ing form
could I be adding? could you be adding? could she be adding? could we be adding? could you be adding? could they be adding?
Perfect
could I have added? could you have added? could she have added? could we have added? could you have added? could they have added?
V-ing perfect
could I have been adding? could you have been adding? could she have been adding? could we have been adding? could you have been adding? could they have been adding?
Interro-negative form
Simple form
couldn't I add? couldn't you add? couldn't she add? couldn't we add? couldn't you add? couldn't they add?
V-ing form
couldn't I be adding? couldn't you be adding? couldn't she be adding? couldn't we be adding? couldn't you be adding? couldn't they be adding?
Perfect
couldn't I have added? couldn't you have added? couldn't she have added? couldn't we have added? couldn't you have added? couldn't they have added?
V-ing perfect
couldn't I have been adding? couldn't you have been adding? couldn't she have been adding? couldn't we have been adding? couldn't you have been adding? couldn't they have been adding?