can challenge
Regular verb: challenge - challenged- challenged

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

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

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

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