can challenge
Regular verb: challenge - challenged- challenged

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