You will be given a definition of a task first, then some input of the task.
In this task, you need to provide the correct option for a given problem on probability from the provided options.

Problem: a multiple choice test consists of 4 questions , and each question has 5 answer choices . in how many ways can the test be completed if every question is unanswered ? 
Options: a ) 24 , b ) 120 , c ) 625 , d ) 720 , e ) 1024
Output:
c