Which of the following violates password best practices?

Password reuse across sites is a major security vulnerability because if one service is breached, an attacker can use those same credentials to access a user's accounts on other services, a technique known as credential stuffing.

Password history, which prevents users from reusing old passwords, is a good security practice.

Password expiration, requiring users to change passwords regularly, is often considered a security best practice, though its effectiveness is debated by some experts in favor of longer, unique passwords managed by password managers.

Password complexity, requiring a mix of uppercase, lowercase, numbers, and special characters, is a fundamental best practice to make passwords harder to guess or crack.