A multiple choice test consists of 4 questions, and each question has 5 answer choices. In how many E ways can the test be completed if every question is unanswered?
Answers:  A) 24  B) 120  C) 625  D) 720  E) 1024

Rationale: "5 choices for each of the 4 questions , thus total e of 5 * 5 * 5 * 5 = 5 ^ 4 = 625 ways to answer all of them . answer : c ."
Answer: C