What does two-factor authentication involve?

Two-factor authentication (2FA) is a security mechanism that requires two different forms of identification to verify a user's identity when accessing an account or system. The correct answer involves using something you know, such as a password, and something you have, like a hardware token or a smartphone application that generates a one-time code. This dual approach enhances security because even if a malicious actor obtains the password (something you know), they would still need the second factor (something you have) to gain access, significantly reducing the risk of unauthorized access.

In contrast, the other options focus on singular forms of verification or combinations that do not meet the criteria for two-factor authentication. For instance, using two passwords or a password and a question does not introduce an additional layer of security from a different category, as both factors would still fall under the same form of identification (knowledge-based). Similarly, a nickname or implicit identifiers do not provide the necessary security that two distinct and independent authentication factors offer.