I could refuel you could refuel she could refuel we could refuel you could refuel they could refuel
V-ing form
I could be refuelling you could be refuelling she could be refuelling we could be refuelling you could be refuelling they could be refuelling
Perfect
I could have refuelled you could have refuelled she could have refuelled we could have refuelled you could have refuelled they could have refuelled
V-ing perfect
I could have been refuelling you could have been refuelling she could have been refuelling we could have been refuelling you could have been refuelling they could have been refuelling
Negation
Simple form
I could not refuel you could not refuel she could not refuel we could not refuel you could not refuel they could not refuel
V-ing form
I could not be refuelling you could not be refuelling she could not be refuelling we could not be refuelling you could not be refuelling they could not be refuelling
Perfect
I could not have refuelled you could not have refuelled she could not have refuelled we could not have refuelled you could not have refuelled they could not have refuelled
V-ing perfect
I could not have been refuelling you could not have been refuelling she could not have been refuelling we could not have been refuelling you could not have been refuelling they could not have been refuelling
Interrogative form
Simple form
could I refuel? could you refuel? could she refuel? could we refuel? could you refuel? could they refuel?
V-ing form
could I be refuelling? could you be refuelling? could she be refuelling? could we be refuelling? could you be refuelling? could they be refuelling?
Perfect
could I have refuelled? could you have refuelled? could she have refuelled? could we have refuelled? could you have refuelled? could they have refuelled?
V-ing perfect
could I have been refuelling? could you have been refuelling? could she have been refuelling? could we have been refuelling? could you have been refuelling? could they have been refuelling?
Interro-negative form
Simple form
could I not refuel? could you not refuel? could she not refuel? could we not refuel? could you not refuel? could they not refuel?
V-ing form
could I not be refuelling? could you not be refuelling? could she not be refuelling? could we not be refuelling? could you not be refuelling? could they not be refuelling?
Perfect
could I not have refuelled? could you not have refuelled? could she not have refuelled? could we not have refuelled? could you not have refuelled? could they not have refuelled?
V-ing perfect
could I not have been refuelling? could you not have been refuelling? could she not have been refuelling? could we not have been refuelling? could you not have been refuelling? could they not have been refuelling?