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