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 couldn't coo you couldn't coo he couldn't coo we couldn't coo you couldn't coo they couldn't coo
V-ing form
I couldn't be cooing you couldn't be cooing he couldn't be cooing we couldn't be cooing you couldn't be cooing they couldn't be cooing
Perfect
I couldn't have cooed you couldn't have cooed he couldn't have cooed we couldn't have cooed you couldn't have cooed they couldn't have cooed
V-ing perfect
I couldn't have been cooing you couldn't have been cooing he couldn't have been cooing we couldn't have been cooing you couldn't have been cooing they couldn't 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
couldn't I coo? couldn't you coo? couldn't he coo? couldn't we coo? couldn't you coo? couldn't they coo?
V-ing form
couldn't I be cooing? couldn't you be cooing? couldn't he be cooing? couldn't we be cooing? couldn't you be cooing? couldn't they be cooing?
Perfect
couldn't I have cooed? couldn't you have cooed? couldn't he have cooed? couldn't we have cooed? couldn't you have cooed? couldn't they have cooed?
V-ing perfect
couldn't I have been cooing? couldn't you have been cooing? couldn't he have been cooing? couldn't we have been cooing? couldn't you have been cooing? couldn't they have been cooing?