English verb conjugation
COULD REFINE

Regular verb: refine - refined - refined

Affirmation

Simple form	V-ing form
I could refine you could refine he could refine we could refine you could refine they could refine	I could be refining you could be refining he could be refining we could be refining you could be refining they could be refining
Perfect	V-ing perfect
I could have refined you could have refined he could have refined we could have refined you could have refined they could have refined	I could have been refining you could have been refining he could have been refining we could have been refining you could have been refining they could have been refining

Negation

Simple form	V-ing form
I couldn't refine you couldn't refine he couldn't refine we couldn't refine you couldn't refine they couldn't refine	I couldn't be refining you couldn't be refining he couldn't be refining we couldn't be refining you couldn't be refining they couldn't be refining
Perfect	V-ing perfect
I couldn't have refined you couldn't have refined he couldn't have refined we couldn't have refined you couldn't have refined they couldn't have refined	I couldn't have been refining you couldn't have been refining he couldn't have been refining we couldn't have been refining you couldn't have been refining they couldn't have been refining

Interrogative form

Simple form	V-ing form
could I refine? could you refine? could he refine? could we refine? could you refine? could they refine?	could I be refining? could you be refining? could he be refining? could we be refining? could you be refining? could they be refining?
Perfect	V-ing perfect
could I have refined? could you have refined? could he have refined? could we have refined? could you have refined? could they have refined?	could I have been refining? could you have been refining? could he have been refining? could we have been refining? could you have been refining? could they have been refining?

Interro-negative form

Simple form	V-ing form
couldn't I refine? couldn't you refine? couldn't he refine? couldn't we refine? couldn't you refine? couldn't they refine?	couldn't I be refining? couldn't you be refining? couldn't he be refining? couldn't we be refining? couldn't you be refining? couldn't they be refining?
Perfect	V-ing perfect
couldn't I have refined? couldn't you have refined? couldn't he have refined? couldn't we have refined? couldn't you have refined? couldn't they have refined?	couldn't I have been refining? couldn't you have been refining? couldn't he have been refining? couldn't we have been refining? couldn't you have been refining? couldn't they have been refining?