A User Boots Up Her Computer,and Instead of Seeing a Login

Multiple Choice

A user boots up her computer,and instead of seeing a login screen,she sees a screen that says "This computer has been infected with a virus.To purchase the removal software for $35 please input your credit card information below." No matter what the user tries,she can't get away from this screen.Which of the following is this an example of?

A) Spyware
B) Trojan
C) Adware
D) Ransomware