Which security measure involves using more than one method of authentication to verify a user's identity?

Multifactor Authentication is the correct answer because it requires users to provide two or more different types of verification to access their accounts or systems. This typically combines something the user knows (like a password), something the user has (like a smartphone or security token), and something the user is (like a fingerprint). By utilizing multiple methods of authentication, multifactor authentication significantly enhances security, making it much more difficult for unauthorized individuals to gain access.

In contrast, the other security measures mentioned serve different purposes. Single Sign-On simplifies the authentication process by allowing users to log in once and gain access to multiple applications without needing to re-enter credentials. Two-Step Verification, while it may sound similar, typically refers to a specific process that might still fall under the broader category of multifactor authentication. Lastly, Password Protection is merely one layer of security that relies solely on the strength of a password, lacking the additional verification involved in multifactor approaches.