could surface
Regular verb: surface - surfaced- surfaced

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could surface
you could surface
he could surface
we could surface
you could surface
they could surface 	I could be surfacing
you could be surfacing
he could be surfacing
we could be surfacing
you could be surfacing
they could be surfacing	I could have surfaced
you could have surfaced
he could have surfaced
we could have surfaced
you could have surfaced
they could have surfaced	I could have been surfacing
you could have been surfacing
he could have been surfacing
we could have been surfacing
you could have been surfacing
they could have been surfacing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't surface
you couldn't surface
he couldn't surface
we couldn't surface
you couldn't surface
they couldn't surface 	I couldn't be surfacing
you couldn't be surfacing
he couldn't be surfacing
we couldn't be surfacing
you couldn't be surfacing
they couldn't be surfacing	I couldn't have surfaced
you couldn't have surfaced
he couldn't have surfaced
we couldn't have surfaced
you couldn't have surfaced
they couldn't have surfaced	I couldn't have been surfacing
you couldn't have been surfacing
he couldn't have been surfacing
we couldn't have been surfacing
you couldn't have been surfacing
they couldn't have been surfacing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I surface?
could you surface?
could he surface?
could we surface?
could you surface?
could they surface? 	could I be surfacing?
could you be surfacing?
could he be surfacing?
could we be surfacing?
could you be surfacing?
could they be surfacing? 	could I have surfaced?
could you have surfaced?
could he have surfaced?
could we have surfaced?
could you have surfaced?
could they have surfaced? 	could I have been surfacing?
could you have been surfacing?
could he have been surfacing?
could we have been surfacing?
could you have been surfacing?
could they have been surfacing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I surface?
couldn't you surface?
couldn't he surface?
couldn't we surface?
couldn't you surface?
couldn't they surface? 	couldn't I be surfacing?
couldn't you be surfacing?
couldn't he be surfacing?
couldn't we be surfacing?
couldn't you be surfacing?
couldn't they be surfacing? 	couldn't I have surfaced?
couldn't you have surfaced?
couldn't he have surfaced?
couldn't we have surfaced?
couldn't you have surfaced?
couldn't they have surfaced? 	couldn't I have been surfacing?
couldn't you have been surfacing?
couldn't he have been surfacing?
couldn't we have been surfacing?
couldn't you have been surfacing?
couldn't they have been surfacing?