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