I could refuel you could refuel he could refuel we could refuel you could refuel they could refuel
V-ing form
I could be refuelling you could be refuelling he could be refuelling we could be refuelling you could be refuelling they could be refuelling
Perfect
I could have refuelled you could have refuelled he 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 he could have been refuelling we could have been refuelling you could have been refuelling they could have been refuelling
Negation
Simple form
I couldn't refuel you couldn't refuel he couldn't refuel we couldn't refuel you couldn't refuel they couldn't refuel
V-ing form
I couldn't be refuelling you couldn't be refuelling he couldn't be refuelling we couldn't be refuelling you couldn't be refuelling they couldn't be refuelling
Perfect
I couldn't have refuelled you couldn't have refuelled he couldn't have refuelled we couldn't have refuelled you couldn't have refuelled they couldn't have refuelled
V-ing perfect
I couldn't have been refuelling you couldn't have been refuelling he couldn't have been refuelling we couldn't have been refuelling you couldn't have been refuelling they couldn't have been refuelling
Interrogative form
Simple form
could I refuel? could you refuel? could he refuel? could we refuel? could you refuel? could they refuel?
V-ing form
could I be refuelling? could you be refuelling? could he be refuelling? could we be refuelling? could you be refuelling? could they be refuelling?
Perfect
could I have refuelled? could you have refuelled? could he 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 he have been refuelling? could we have been refuelling? could you have been refuelling? could they have been refuelling?
Interro-negative form
Simple form
couldn't I refuel? couldn't you refuel? couldn't he refuel? couldn't we refuel? couldn't you refuel? couldn't they refuel?
V-ing form
couldn't I be refuelling? couldn't you be refuelling? couldn't he be refuelling? couldn't we be refuelling? couldn't you be refuelling? couldn't they be refuelling?
Perfect
couldn't I have refuelled? couldn't you have refuelled? couldn't he have refuelled? couldn't we have refuelled? couldn't you have refuelled? couldn't they have refuelled?
V-ing perfect
couldn't I have been refuelling? couldn't you have been refuelling? couldn't he have been refuelling? couldn't we have been refuelling? couldn't you have been refuelling? couldn't they have been refuelling?