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