must toughen
Regular verb: toughen - toughened- toughened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must toughen
you must toughen
she must toughen
we must toughen
you must toughen
they must toughen 	I must be toughening
you must be toughening
she must be toughening
we must be toughening
you must be toughening
they must be toughening	I must have toughened
you must have toughened
she must have toughened
we must have toughened
you must have toughened
they must have toughened	I must have been toughening
you must have been toughening
she must have been toughening
we must have been toughening
you must have been toughening
they must have been toughening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't toughen
you mustn't toughen
she mustn't toughen
we mustn't toughen
you mustn't toughen
they mustn't toughen 	I mustn't be toughening
you mustn't be toughening
she mustn't be toughening
we mustn't be toughening
you mustn't be toughening
they mustn't be toughening	I mustn't have toughened
you mustn't have toughened
she mustn't have toughened
we mustn't have toughened
you mustn't have toughened
they mustn't have toughened	I mustn't have been toughening
you mustn't have been toughening
she mustn't have been toughening
we mustn't have been toughening
you mustn't have been toughening
they mustn't have been toughening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I toughen?
must you toughen?
must she toughen?
must we toughen?
must you toughen?
must they toughen? 	must I be toughening?
must you be toughening?
must she be toughening?
must we be toughening?
must you be toughening?
must they be toughening? 	must I have toughened?
must you have toughened?
must she have toughened?
must we have toughened?
must you have toughened?
must they have toughened? 	must I have been toughening?
must you have been toughening?
must she have been toughening?
must we have been toughening?
must you have been toughening?
must they have been toughening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I toughen?
mustn't you toughen?
mustn't she toughen?
mustn't we toughen?
mustn't you toughen?
mustn't they toughen? 	mustn't I be toughening?
mustn't you be toughening?
mustn't she be toughening?
mustn't we be toughening?
mustn't you be toughening?
mustn't they be toughening? 	mustn't I have toughened?
mustn't you have toughened?
mustn't she have toughened?
mustn't we have toughened?
mustn't you have toughened?
mustn't they have toughened? 	mustn't I have been toughening?
mustn't you have been toughening?
mustn't she have been toughening?
mustn't we have been toughening?
mustn't you have been toughening?
mustn't they have been toughening?