could refine
Regular verb: refine - refined- refined

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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	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 	Perfect 	V-ing perfect 	
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	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 	Perfect 	V-ing perfect 	
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? 	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 	Perfect 	V-ing perfect 	
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? 	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?