Which of the following is NOT listed as a type of authentication?

• A. Basic (password)
• B. Digest
• C. Biometrics
• D. Token-based

Answer: (D)

Authentication methods are ways to prove who you are. Basic is the classic username and password approach. Digest is a challenge-response scheme used in HTTP to avoid sending the password in clear text. Biometrics relies on something intrinsic to the user, like a fingerprint or iris scan. Token-based is commonly used as a credential in practice, but in this set of listed authentication types it isn’t presented as a standalone authentication method; it’s more often discussed as a credential or as part of authorization/session management rather than a primary authentication type in this context. So the option describing token-based doesn’t fit the listed authentication types in this question’s framework.