present
I challenge
You challenge
He challenges
She challenges
It challenges
We challenge
They challenge
past
I challenged
You challenged
He challenged
She challenged
It challenged
We challenged
They challenged
future
I will challenge
You will challenge
He will challenge
She will challenge
It will challenge
We will challenge
They will challenge
conditional
I would challenge
You would challenge
He would challenge
She would challenge
It would challenge
We would challenge
They would challenge