I could surface you could surface he could surface we could surface you could surface they could surface
V-ing form
I could be surfacing you could be surfacing he could be surfacing we could be surfacing you could be surfacing they could be surfacing
Perfect
I could have surfaced you could have surfaced he could have surfaced we could have surfaced you could have surfaced they could have surfaced
V-ing perfect
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
I could not surface you could not surface he could not surface we could not surface you could not surface they could not surface
V-ing form
I could not be surfacing you could not be surfacing he could not be surfacing we could not be surfacing you could not be surfacing they could not be surfacing
Perfect
I could not have surfaced you could not have surfaced he could not have surfaced we could not have surfaced you could not have surfaced they could not have surfaced
V-ing perfect
I could not have been surfacing you could not have been surfacing he could not have been surfacing we could not have been surfacing you could not have been surfacing they could not have been surfacing
Interrogative form
Simple form
could I surface? could you surface? could he surface? could we surface? could you surface? could they surface?
V-ing form
could I be surfacing? could you be surfacing? could he be surfacing? could we be surfacing? could you be surfacing? could they be surfacing?
Perfect
could I have surfaced? could you have surfaced? could he have surfaced? could we have surfaced? could you have surfaced? could they have surfaced?
V-ing perfect
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
could I not surface? could you not surface? could he not surface? could we not surface? could you not surface? could they not surface?
V-ing form
could I not be surfacing? could you not be surfacing? could he not be surfacing? could we not be surfacing? could you not be surfacing? could they not be surfacing?
Perfect
could I not have surfaced? could you not have surfaced? could he not have surfaced? could we not have surfaced? could you not have surfaced? could they not have surfaced?
V-ing perfect
could I not have been surfacing? could you not have been surfacing? could he not have been surfacing? could we not have been surfacing? could you not have been surfacing? could they not have been surfacing?