I could ret you could ret he could ret we could ret you could ret they could ret
V-ing form
I could be retting you could be retting he could be retting we could be retting you could be retting they could be retting
Perfect
I could have retted you could have retted he could have retted we could have retted you could have retted they could have retted
V-ing perfect
I could have been retting you could have been retting he could have been retting we could have been retting you could have been retting they could have been retting
Negation
Simple form
I could not ret you could not ret he could not ret we could not ret you could not ret they could not ret
V-ing form
I could not be retting you could not be retting he could not be retting we could not be retting you could not be retting they could not be retting
Perfect
I could not have retted you could not have retted he could not have retted we could not have retted you could not have retted they could not have retted
V-ing perfect
I could not have been retting you could not have been retting he could not have been retting we could not have been retting you could not have been retting they could not have been retting
Interrogative form
Simple form
could I ret? could you ret? could he ret? could we ret? could you ret? could they ret?
V-ing form
could I be retting? could you be retting? could he be retting? could we be retting? could you be retting? could they be retting?
Perfect
could I have retted? could you have retted? could he have retted? could we have retted? could you have retted? could they have retted?
V-ing perfect
could I have been retting? could you have been retting? could he have been retting? could we have been retting? could you have been retting? could they have been retting?
Interro-negative form
Simple form
could I not ret? could you not ret? could he not ret? could we not ret? could you not ret? could they not ret?
V-ing form
could I not be retting? could you not be retting? could he not be retting? could we not be retting? could you not be retting? could they not be retting?
Perfect
could I not have retted? could you not have retted? could he not have retted? could we not have retted? could you not have retted? could they not have retted?
V-ing perfect
could I not have been retting? could you not have been retting? could he not have been retting? could we not have been retting? could you not have been retting? could they not have been retting?