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