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