I must prevent you must prevent she must prevent we must prevent you must prevent they must prevent
V-ing form
I must be preventing you must be preventing she must be preventing we must be preventing you must be preventing they must be preventing
Perfect
I must have prevented you must have prevented she must have prevented we must have prevented you must have prevented they must have prevented
V-ing perfect
I must have been preventing you must have been preventing she must have been preventing we must have been preventing you must have been preventing they must have been preventing
Negation
Simple form
I mustn't prevent you mustn't prevent she mustn't prevent we mustn't prevent you mustn't prevent they mustn't prevent
V-ing form
I mustn't be preventing you mustn't be preventing she mustn't be preventing we mustn't be preventing you mustn't be preventing they mustn't be preventing
Perfect
I mustn't have prevented you mustn't have prevented she mustn't have prevented we mustn't have prevented you mustn't have prevented they mustn't have prevented
V-ing perfect
I mustn't have been preventing you mustn't have been preventing she mustn't have been preventing we mustn't have been preventing you mustn't have been preventing they mustn't have been preventing
Interrogative form
Simple form
must I prevent? must you prevent? must she prevent? must we prevent? must you prevent? must they prevent?
V-ing form
must I be preventing? must you be preventing? must she be preventing? must we be preventing? must you be preventing? must they be preventing?
Perfect
must I have prevented? must you have prevented? must she have prevented? must we have prevented? must you have prevented? must they have prevented?
V-ing perfect
must I have been preventing? must you have been preventing? must she have been preventing? must we have been preventing? must you have been preventing? must they have been preventing?
Interro-negative form
Simple form
mustn't I prevent? mustn't you prevent? mustn't she prevent? mustn't we prevent? mustn't you prevent? mustn't they prevent?
V-ing form
mustn't I be preventing? mustn't you be preventing? mustn't she be preventing? mustn't we be preventing? mustn't you be preventing? mustn't they be preventing?
Perfect
mustn't I have prevented? mustn't you have prevented? mustn't she have prevented? mustn't we have prevented? mustn't you have prevented? mustn't they have prevented?
V-ing perfect
mustn't I have been preventing? mustn't you have been preventing? mustn't she have been preventing? mustn't we have been preventing? mustn't you have been preventing? mustn't they have been preventing?