English verb conjugation
COULD PREVENT

Regular verb: prevent - prevented - prevented

Affirmation

Simple form	V-ing form
I could prevent you could prevent she could prevent we could prevent you could prevent they could prevent	I could be preventing you could be preventing she could be preventing we could be preventing you could be preventing they could be preventing
Perfect	V-ing perfect
I could have prevented you could have prevented she could have prevented we could have prevented you could have prevented they could have prevented	I could have been preventing you could have been preventing she could have been preventing we could have been preventing you could have been preventing they could have been preventing

Negation

Simple form	V-ing form
I could not prevent you could not prevent she could not prevent we could not prevent you could not prevent they could not prevent	I could not be preventing you could not be preventing she could not be preventing we could not be preventing you could not be preventing they could not be preventing
Perfect	V-ing perfect
I could not have prevented you could not have prevented she could not have prevented we could not have prevented you could not have prevented they could not have prevented	I could not have been preventing you could not have been preventing she could not have been preventing we could not have been preventing you could not have been preventing they could not have been preventing

Interrogative form

Simple form	V-ing form
could I prevent? could you prevent? could she prevent? could we prevent? could you prevent? could they prevent?	could I be preventing? could you be preventing? could she be preventing? could we be preventing? could you be preventing? could they be preventing?
Perfect	V-ing perfect
could I have prevented? could you have prevented? could she have prevented? could we have prevented? could you have prevented? could they have prevented?	could I have been preventing? could you have been preventing? could she have been preventing? could we have been preventing? could you have been preventing? could they have been preventing?

Interro-negative form

Simple form	V-ing form
could I not prevent? could you not prevent? could she not prevent? could we not prevent? could you not prevent? could they not prevent?	could I not be preventing? could you not be preventing? could she not be preventing? could we not be preventing? could you not be preventing? could they not be preventing?
Perfect	V-ing perfect
could I not have prevented? could you not have prevented? could she not have prevented? could we not have prevented? could you not have prevented? could they not have prevented?	could I not have been preventing? could you not have been preventing? could she not have been preventing? could we not have been preventing? could you not have been preventing? could they not have been preventing?