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