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