Which of the following is an example of ransomware?

This scenario perfectly describes ransomware, where an attacker encrypts a user's files and demands a ransom (the 'fee for a password') to provide the decryption key, thereby unlocking access to the files. This direct form of extortion for data access is the hallmark of ransomware.

An email demanding payment for a trial application is more indicative of a scam or phishing attempt, not the file-locking mechanism of ransomware.

Being redirected to an unfamiliar website indicates browser hijacking or a potentially unwanted program (PUP), not the encryption and ransom demand of ransomware.

Being asked to open an attachment that verifies an un-ordered item is a common tactic for phishing or distributing malware, but not specifically ransomware's direct demand for payment to unlock files.