I could rub you could rub he could rub we could rub you could rub they could rub
V-ing form
I could be rubbing you could be rubbing he could be rubbing we could be rubbing you could be rubbing they could be rubbing
Perfect
I could have rubbed you could have rubbed he could have rubbed we could have rubbed you could have rubbed they could have rubbed
V-ing perfect
I could have been rubbing you could have been rubbing he could have been rubbing we could have been rubbing you could have been rubbing they could have been rubbing
Negation
Simple form
I could not rub you could not rub he could not rub we could not rub you could not rub they could not rub
V-ing form
I could not be rubbing you could not be rubbing he could not be rubbing we could not be rubbing you could not be rubbing they could not be rubbing
Perfect
I could not have rubbed you could not have rubbed he could not have rubbed we could not have rubbed you could not have rubbed they could not have rubbed
V-ing perfect
I could not have been rubbing you could not have been rubbing he could not have been rubbing we could not have been rubbing you could not have been rubbing they could not have been rubbing
Interrogative form
Simple form
could I rub? could you rub? could he rub? could we rub? could you rub? could they rub?
V-ing form
could I be rubbing? could you be rubbing? could he be rubbing? could we be rubbing? could you be rubbing? could they be rubbing?
Perfect
could I have rubbed? could you have rubbed? could he have rubbed? could we have rubbed? could you have rubbed? could they have rubbed?
V-ing perfect
could I have been rubbing? could you have been rubbing? could he have been rubbing? could we have been rubbing? could you have been rubbing? could they have been rubbing?
Interro-negative form
Simple form
could I not rub? could you not rub? could he not rub? could we not rub? could you not rub? could they not rub?
V-ing form
could I not be rubbing? could you not be rubbing? could he not be rubbing? could we not be rubbing? could you not be rubbing? could they not be rubbing?
Perfect
could I not have rubbed? could you not have rubbed? could he not have rubbed? could we not have rubbed? could you not have rubbed? could they not have rubbed?
V-ing perfect
could I not have been rubbing? could you not have been rubbing? could he not have been rubbing? could we not have been rubbing? could you not have been rubbing? could they not have been rubbing?