I could ko you could ko he could ko we could ko you could ko they could ko
V-ing form
I could be koing you could be koing he could be koing we could be koing you could be koing they could be koing
Perfect
I could have koed you could have koed he could have koed we could have koed you could have koed they could have koed
V-ing perfect
I could have been koing you could have been koing he could have been koing we could have been koing you could have been koing they could have been koing
Negation
Simple form
I could not ko you could not ko he could not ko we could not ko you could not ko they could not ko
V-ing form
I could not be koing you could not be koing he could not be koing we could not be koing you could not be koing they could not be koing
Perfect
I could not have koed you could not have koed he could not have koed we could not have koed you could not have koed they could not have koed
V-ing perfect
I could not have been koing you could not have been koing he could not have been koing we could not have been koing you could not have been koing they could not have been koing
Interrogative form
Simple form
could I ko? could you ko? could he ko? could we ko? could you ko? could they ko?
V-ing form
could I be koing? could you be koing? could he be koing? could we be koing? could you be koing? could they be koing?
Perfect
could I have koed? could you have koed? could he have koed? could we have koed? could you have koed? could they have koed?
V-ing perfect
could I have been koing? could you have been koing? could he have been koing? could we have been koing? could you have been koing? could they have been koing?
Interro-negative form
Simple form
could I not ko? could you not ko? could he not ko? could we not ko? could you not ko? could they not ko?
V-ing form
could I not be koing? could you not be koing? could he not be koing? could we not be koing? could you not be koing? could they not be koing?
Perfect
could I not have koed? could you not have koed? could he not have koed? could we not have koed? could you not have koed? could they not have koed?
V-ing perfect
could I not have been koing? could you not have been koing? could he not have been koing? could we not have been koing? could you not have been koing? could they not have been koing?