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