I'd be preventing you'd be preventing he'd be preventing we'd be preventing you'd be preventing they'd be preventing
Perfect
I should've prevented you should've prevented he should've prevented we should've prevented you should've prevented they should've prevented
V-ing perfect
I should've been preventing you should've been preventing he should've been preventing we should've been preventing you should've been preventing they should've been preventing
Negation
Simple form
I shouldn't prevent you shouldn't prevent he shouldn't prevent we shouldn't prevent you shouldn't prevent they shouldn't prevent
V-ing form
I shouldn't be preventing you shouldn't be preventing he shouldn't be preventing we shouldn't be preventing you shouldn't be preventing they shouldn't be preventing
Perfect
I shouldn't have prevented you shouldn't have prevented he shouldn't have prevented we shouldn't have prevented you shouldn't have prevented they shouldn't have prevented
V-ing perfect
I shouldn't have been preventing you shouldn't have been preventing he shouldn't have been preventing we shouldn't have been preventing you shouldn't have been preventing they shouldn't have been preventing
Interrogative form
Simple form
should I prevent? should you prevent? should he prevent? should we prevent? should you prevent? should they prevent?
V-ing form
should I be preventing? should you be preventing? should he be preventing? should we be preventing? should you be preventing? should they be preventing?
Perfect
should I have prevented? should you have prevented? should he have prevented? should we have prevented? should you have prevented? should they have prevented?
V-ing perfect
should I have been preventing? should you have been preventing? should he have been preventing? should we have been preventing? should you have been preventing? should they have been preventing?
Interro-negative form
Simple form
shouldn't I prevent? shouldn't you prevent? shouldn't he prevent? shouldn't we prevent? shouldn't you prevent? shouldn't they prevent?
V-ing form
shouldn't I be preventing? shouldn't you be preventing? shouldn't he be preventing? shouldn't we be preventing? shouldn't you be preventing? shouldn't they be preventing?
Perfect
shouldn't I have prevented? shouldn't you have prevented? shouldn't he have prevented? shouldn't we have prevented? shouldn't you have prevented? shouldn't they have prevented?
V-ing perfect
shouldn't I have been preventing? shouldn't you have been preventing? shouldn't he have been preventing? shouldn't we have been preventing? shouldn't you have been preventing? shouldn't they have been preventing?