Which security mechanism provides an additional factor beyond password to verify identity?

• A. Password-Based Authentication
• B. Biometric-Only Authentication
• C. Single-Factor Authentication
• D. Two-Factor Authentication

Answer: (D)

Using two separate verification methods to prove identity is required. A password is one factor (something you know). Adding an extra factor—such as something you have (a code from an authenticator app or a hardware token) or something you are (a biometric)—gives two-factor authentication. This approach strengthens security because the second factor remains even if the password is compromised. The other options describe only a single factor: password-based authentication relies solely on a password; biometric-only authentication relies on a biometric measurement alone; and single-factor authentication covers any method using just one factor, which doesn’t meet the requirement of adding a second factor.