I must behave you must behave he must behave we must behave you must behave they must behave
V-ing form
I must be behaving you must be behaving he must be behaving we must be behaving you must be behaving they must be behaving
Perfect
I must have behaved you must have behaved he must have behaved we must have behaved you must have behaved they must have behaved
V-ing perfect
I must have been behaving you must have been behaving he must have been behaving we must have been behaving you must have been behaving they must have been behaving
Negation
Simple form
I mustn't behave you mustn't behave he mustn't behave we mustn't behave you mustn't behave they mustn't behave
V-ing form
I mustn't be behaving you mustn't be behaving he mustn't be behaving we mustn't be behaving you mustn't be behaving they mustn't be behaving
Perfect
I mustn't have behaved you mustn't have behaved he mustn't have behaved we mustn't have behaved you mustn't have behaved they mustn't have behaved
V-ing perfect
I mustn't have been behaving you mustn't have been behaving he mustn't have been behaving we mustn't have been behaving you mustn't have been behaving they mustn't have been behaving
Interrogative form
Simple form
must I behave? must you behave? must he behave? must we behave? must you behave? must they behave?
V-ing form
must I be behaving? must you be behaving? must he be behaving? must we be behaving? must you be behaving? must they be behaving?
Perfect
must I have behaved? must you have behaved? must he have behaved? must we have behaved? must you have behaved? must they have behaved?
V-ing perfect
must I have been behaving? must you have been behaving? must he have been behaving? must we have been behaving? must you have been behaving? must they have been behaving?
Interro-negative form
Simple form
mustn't I behave? mustn't you behave? mustn't he behave? mustn't we behave? mustn't you behave? mustn't they behave?
V-ing form
mustn't I be behaving? mustn't you be behaving? mustn't he be behaving? mustn't we be behaving? mustn't you be behaving? mustn't they be behaving?
Perfect
mustn't I have behaved? mustn't you have behaved? mustn't he have behaved? mustn't we have behaved? mustn't you have behaved? mustn't they have behaved?
V-ing perfect
mustn't I have been behaving? mustn't you have been behaving? mustn't he have been behaving? mustn't we have been behaving? mustn't you have been behaving? mustn't they have been behaving?