English verb conjugation
COULD JACKKNIFE

Regular verb: jackknife - jackknifed - jackknifed

Affirmation

Simple form	V-ing form
I could jackknife you could jackknife he could jackknife we could jackknife you could jackknife they could jackknife	I could be jackknifing you could be jackknifing he could be jackknifing we could be jackknifing you could be jackknifing they could be jackknifing
Perfect	V-ing perfect
I could have jackknifed you could have jackknifed he could have jackknifed we could have jackknifed you could have jackknifed they could have jackknifed	I could have been jackknifing you could have been jackknifing he could have been jackknifing we could have been jackknifing you could have been jackknifing they could have been jackknifing

Negation

Simple form	V-ing form
I couldn't jackknife you couldn't jackknife he couldn't jackknife we couldn't jackknife you couldn't jackknife they couldn't jackknife	I couldn't be jackknifing you couldn't be jackknifing he couldn't be jackknifing we couldn't be jackknifing you couldn't be jackknifing they couldn't be jackknifing
Perfect	V-ing perfect
I couldn't have jackknifed you couldn't have jackknifed he couldn't have jackknifed we couldn't have jackknifed you couldn't have jackknifed they couldn't have jackknifed	I couldn't have been jackknifing you couldn't have been jackknifing he couldn't have been jackknifing we couldn't have been jackknifing you couldn't have been jackknifing they couldn't have been jackknifing

Interrogative form

Simple form	V-ing form
could I jackknife? could you jackknife? could he jackknife? could we jackknife? could you jackknife? could they jackknife?	could I be jackknifing? could you be jackknifing? could he be jackknifing? could we be jackknifing? could you be jackknifing? could they be jackknifing?
Perfect	V-ing perfect
could I have jackknifed? could you have jackknifed? could he have jackknifed? could we have jackknifed? could you have jackknifed? could they have jackknifed?	could I have been jackknifing? could you have been jackknifing? could he have been jackknifing? could we have been jackknifing? could you have been jackknifing? could they have been jackknifing?

Interro-negative form

Simple form	V-ing form
couldn't I jackknife? couldn't you jackknife? couldn't he jackknife? couldn't we jackknife? couldn't you jackknife? couldn't they jackknife?	couldn't I be jackknifing? couldn't you be jackknifing? couldn't he be jackknifing? couldn't we be jackknifing? couldn't you be jackknifing? couldn't they be jackknifing?
Perfect	V-ing perfect
couldn't I have jackknifed? couldn't you have jackknifed? couldn't he have jackknifed? couldn't we have jackknifed? couldn't you have jackknifed? couldn't they have jackknifed?	couldn't I have been jackknifing? couldn't you have been jackknifing? couldn't he have been jackknifing? couldn't we have been jackknifing? couldn't you have been jackknifing? couldn't they have been jackknifing?