must chuff
Regular verb: chuff - chuffed- chuffed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must chuff
you must chuff
she must chuff
we must chuff
you must chuff
they must chuff 	I must be chuffing
you must be chuffing
she must be chuffing
we must be chuffing
you must be chuffing
they must be chuffing	I must have chuffed
you must have chuffed
she must have chuffed
we must have chuffed
you must have chuffed
they must have chuffed	I must have been chuffing
you must have been chuffing
she must have been chuffing
we must have been chuffing
you must have been chuffing
they must have been chuffing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't chuff
you mustn't chuff
she mustn't chuff
we mustn't chuff
you mustn't chuff
they mustn't chuff 	I mustn't be chuffing
you mustn't be chuffing
she mustn't be chuffing
we mustn't be chuffing
you mustn't be chuffing
they mustn't be chuffing	I mustn't have chuffed
you mustn't have chuffed
she mustn't have chuffed
we mustn't have chuffed
you mustn't have chuffed
they mustn't have chuffed	I mustn't have been chuffing
you mustn't have been chuffing
she mustn't have been chuffing
we mustn't have been chuffing
you mustn't have been chuffing
they mustn't have been chuffing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I chuff?
must you chuff?
must she chuff?
must we chuff?
must you chuff?
must they chuff? 	must I be chuffing?
must you be chuffing?
must she be chuffing?
must we be chuffing?
must you be chuffing?
must they be chuffing? 	must I have chuffed?
must you have chuffed?
must she have chuffed?
must we have chuffed?
must you have chuffed?
must they have chuffed? 	must I have been chuffing?
must you have been chuffing?
must she have been chuffing?
must we have been chuffing?
must you have been chuffing?
must they have been chuffing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I chuff?
mustn't you chuff?
mustn't she chuff?
mustn't we chuff?
mustn't you chuff?
mustn't they chuff? 	mustn't I be chuffing?
mustn't you be chuffing?
mustn't she be chuffing?
mustn't we be chuffing?
mustn't you be chuffing?
mustn't they be chuffing? 	mustn't I have chuffed?
mustn't you have chuffed?
mustn't she have chuffed?
mustn't we have chuffed?
mustn't you have chuffed?
mustn't they have chuffed? 	mustn't I have been chuffing?
mustn't you have been chuffing?
mustn't she have been chuffing?
mustn't we have been chuffing?
mustn't you have been chuffing?
mustn't they have been chuffing?