I could coo you could coo he could coo we could coo you could coo they could coo
V-ing form
I could be cooing you could be cooing he could be cooing we could be cooing you could be cooing they could be cooing
Perfect
I could have cooed you could have cooed he could have cooed we could have cooed you could have cooed they could have cooed
V-ing perfect
I could have been cooing you could have been cooing he could have been cooing we could have been cooing you could have been cooing they could have been cooing
Negation
Simple form
I could not coo you could not coo he could not coo we could not coo you could not coo they could not coo
V-ing form
I could not be cooing you could not be cooing he could not be cooing we could not be cooing you could not be cooing they could not be cooing
Perfect
I could not have cooed you could not have cooed he could not have cooed we could not have cooed you could not have cooed they could not have cooed
V-ing perfect
I could not have been cooing you could not have been cooing he could not have been cooing we could not have been cooing you could not have been cooing they could not have been cooing
Interrogative form
Simple form
could I coo? could you coo? could he coo? could we coo? could you coo? could they coo?
V-ing form
could I be cooing? could you be cooing? could he be cooing? could we be cooing? could you be cooing? could they be cooing?
Perfect
could I have cooed? could you have cooed? could he have cooed? could we have cooed? could you have cooed? could they have cooed?
V-ing perfect
could I have been cooing? could you have been cooing? could he have been cooing? could we have been cooing? could you have been cooing? could they have been cooing?
Interro-negative form
Simple form
could I not coo? could you not coo? could he not coo? could we not coo? could you not coo? could they not coo?
V-ing form
could I not be cooing? could you not be cooing? could he not be cooing? could we not be cooing? could you not be cooing? could they not be cooing?
Perfect
could I not have cooed? could you not have cooed? could he not have cooed? could we not have cooed? could you not have cooed? could they not have cooed?
V-ing perfect
could I not have been cooing? could you not have been cooing? could he not have been cooing? could we not have been cooing? could you not have been cooing? could they not have been cooing?