English verb conjugation
COULD RUB

Regular verb: rub - rubbed - rubbed

Affirmation

Simple form	V-ing form
I could rub you could rub she could rub we could rub you could rub they could rub	I could be rubbing you could be rubbing she could be rubbing we could be rubbing you could be rubbing they could be rubbing
Perfect	V-ing perfect
I could have rubbed you could have rubbed she could have rubbed we could have rubbed you could have rubbed they could have rubbed	I could have been rubbing you could have been rubbing she could have been rubbing we could have been rubbing you could have been rubbing they could have been rubbing

Negation

Simple form	V-ing form
I couldn't rub you couldn't rub she couldn't rub we couldn't rub you couldn't rub they couldn't rub	I couldn't be rubbing you couldn't be rubbing she couldn't be rubbing we couldn't be rubbing you couldn't be rubbing they couldn't be rubbing
Perfect	V-ing perfect
I couldn't have rubbed you couldn't have rubbed she couldn't have rubbed we couldn't have rubbed you couldn't have rubbed they couldn't have rubbed	I couldn't have been rubbing you couldn't have been rubbing she couldn't have been rubbing we couldn't have been rubbing you couldn't have been rubbing they couldn't have been rubbing

Interrogative form

Simple form	V-ing form
could I rub? could you rub? could she rub? could we rub? could you rub? could they rub?	could I be rubbing? could you be rubbing? could she be rubbing? could we be rubbing? could you be rubbing? could they be rubbing?
Perfect	V-ing perfect
could I have rubbed? could you have rubbed? could she have rubbed? could we have rubbed? could you have rubbed? could they have rubbed?	could I have been rubbing? could you have been rubbing? could she have been rubbing? could we have been rubbing? could you have been rubbing? could they have been rubbing?

Interro-negative form

Simple form	V-ing form
couldn't I rub? couldn't you rub? couldn't she rub? couldn't we rub? couldn't you rub? couldn't they rub?	couldn't I be rubbing? couldn't you be rubbing? couldn't she be rubbing? couldn't we be rubbing? couldn't you be rubbing? couldn't they be rubbing?
Perfect	V-ing perfect
couldn't I have rubbed? couldn't you have rubbed? couldn't she have rubbed? couldn't we have rubbed? couldn't you have rubbed? couldn't they have rubbed?	couldn't I have been rubbing? couldn't you have been rubbing? couldn't she have been rubbing? couldn't we have been rubbing? couldn't you have been rubbing? couldn't they have been rubbing?