I could undo you could undo she could undo we could undo you could undo they could undo
V-ing form
I could be undoing you could be undoing she could be undoing we could be undoing you could be undoing they could be undoing
Perfect
I could have undone you could have undone she could have undone we could have undone you could have undone they could have undone
V-ing perfect
I could have been undoing you could have been undoing she could have been undoing we could have been undoing you could have been undoing they could have been undoing
Negation
Simple form
I could not undo you could not undo she could not undo we could not undo you could not undo they could not undo
V-ing form
I could not be undoing you could not be undoing she could not be undoing we could not be undoing you could not be undoing they could not be undoing
Perfect
I could not have undone you could not have undone she could not have undone we could not have undone you could not have undone they could not have undone
V-ing perfect
I could not have been undoing you could not have been undoing she could not have been undoing we could not have been undoing you could not have been undoing they could not have been undoing
Interrogative form
Simple form
could I undo? could you undo? could she undo? could we undo? could you undo? could they undo?
V-ing form
could I be undoing? could you be undoing? could she be undoing? could we be undoing? could you be undoing? could they be undoing?
Perfect
could I have undone? could you have undone? could she have undone? could we have undone? could you have undone? could they have undone?
V-ing perfect
could I have been undoing? could you have been undoing? could she have been undoing? could we have been undoing? could you have been undoing? could they have been undoing?
Interro-negative form
Simple form
could I not undo? could you not undo? could she not undo? could we not undo? could you not undo? could they not undo?
V-ing form
could I not be undoing? could you not be undoing? could she not be undoing? could we not be undoing? could you not be undoing? could they not be undoing?
Perfect
could I not have undone? could you not have undone? could she not have undone? could we not have undone? could you not have undone? could they not have undone?
V-ing perfect
could I not have been undoing? could you not have been undoing? could she not have been undoing? could we not have been undoing? could you not have been undoing? could they not have been undoing?