Which of the following is an example of ransomware?

Which of the following is an example of ransomware?

A.
A user is asked to pay a fee for a password to unlock access to their files.

B.
A user receives an email demanding payment for a trial application that has stopped working.

C.
A user has opened an Internet browser and is taken to a site that is not the normal home page.

D.
A user is asked to open an attachment that verifies the price of an item that was not ordered.