must challenge
Regular verb: challenge - challenged- challenged

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must challenge
you must challenge
she must challenge
we must challenge
you must challenge
they must challenge 	I must be challenging
you must be challenging
she must be challenging
we must be challenging
you must be challenging
they must be challenging	I must have challenged
you must have challenged
she must have challenged
we must have challenged
you must have challenged
they must have challenged	I must have been challenging
you must have been challenging
she must have been challenging
we must have been challenging
you must have been challenging
they must have been challenging	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't challenge
you mustn't challenge
she mustn't challenge
we mustn't challenge
you mustn't challenge
they mustn't challenge 	I mustn't be challenging
you mustn't be challenging
she mustn't be challenging
we mustn't be challenging
you mustn't be challenging
they mustn't be challenging	I mustn't have challenged
you mustn't have challenged
she mustn't have challenged
we mustn't have challenged
you mustn't have challenged
they mustn't have challenged	I mustn't have been challenging
you mustn't have been challenging
she mustn't have been challenging
we mustn't have been challenging
you mustn't have been challenging
they mustn't have been challenging	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I challenge?
must you challenge?
must she challenge?
must we challenge?
must you challenge?
must they challenge? 	must I be challenging?
must you be challenging?
must she be challenging?
must we be challenging?
must you be challenging?
must they be challenging? 	must I have challenged?
must you have challenged?
must she have challenged?
must we have challenged?
must you have challenged?
must they have challenged? 	must I have been challenging?
must you have been challenging?
must she have been challenging?
must we have been challenging?
must you have been challenging?
must they have been challenging? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I challenge?
mustn't you challenge?
mustn't she challenge?
mustn't we challenge?
mustn't you challenge?
mustn't they challenge? 	mustn't I be challenging?
mustn't you be challenging?
mustn't she be challenging?
mustn't we be challenging?
mustn't you be challenging?
mustn't they be challenging? 	mustn't I have challenged?
mustn't you have challenged?
mustn't she have challenged?
mustn't we have challenged?
mustn't you have challenged?
mustn't they have challenged? 	mustn't I have been challenging?
mustn't you have been challenging?
mustn't she have been challenging?
mustn't we have been challenging?
mustn't you have been challenging?
mustn't they have been challenging?