English verb conjugation
COULD MAINTAIN

Regular verb: maintain - maintained - maintained

Affirmation

Simple form	V-ing form
I could maintain you could maintain he could maintain we could maintain you could maintain they could maintain	I could be maintaining you could be maintaining he could be maintaining we could be maintaining you could be maintaining they could be maintaining
Perfect	V-ing perfect
I could have maintained you could have maintained he could have maintained we could have maintained you could have maintained they could have maintained	I could have been maintaining you could have been maintaining he could have been maintaining we could have been maintaining you could have been maintaining they could have been maintaining

Negation

Simple form	V-ing form
I couldn't maintain you couldn't maintain he couldn't maintain we couldn't maintain you couldn't maintain they couldn't maintain	I couldn't be maintaining you couldn't be maintaining he couldn't be maintaining we couldn't be maintaining you couldn't be maintaining they couldn't be maintaining
Perfect	V-ing perfect
I couldn't have maintained you couldn't have maintained he couldn't have maintained we couldn't have maintained you couldn't have maintained they couldn't have maintained	I couldn't have been maintaining you couldn't have been maintaining he couldn't have been maintaining we couldn't have been maintaining you couldn't have been maintaining they couldn't have been maintaining

Interrogative form

Simple form	V-ing form
could I maintain? could you maintain? could he maintain? could we maintain? could you maintain? could they maintain?	could I be maintaining? could you be maintaining? could he be maintaining? could we be maintaining? could you be maintaining? could they be maintaining?
Perfect	V-ing perfect
could I have maintained? could you have maintained? could he have maintained? could we have maintained? could you have maintained? could they have maintained?	could I have been maintaining? could you have been maintaining? could he have been maintaining? could we have been maintaining? could you have been maintaining? could they have been maintaining?

Interro-negative form

Simple form	V-ing form
couldn't I maintain? couldn't you maintain? couldn't he maintain? couldn't we maintain? couldn't you maintain? couldn't they maintain?	couldn't I be maintaining? couldn't you be maintaining? couldn't he be maintaining? couldn't we be maintaining? couldn't you be maintaining? couldn't they be maintaining?
Perfect	V-ing perfect
couldn't I have maintained? couldn't you have maintained? couldn't he have maintained? couldn't we have maintained? couldn't you have maintained? couldn't they have maintained?	couldn't I have been maintaining? couldn't you have been maintaining? couldn't he have been maintaining? couldn't we have been maintaining? couldn't you have been maintaining? couldn't they have been maintaining?