What authentication factor does biometric authentication primarily rely on?

Biometric authentication primarily relies on "something you are" because it is based on the unique physical characteristics of the individual. This can include features such as fingerprints, facial recognition, iris scans, and voice recognition. Each of these characteristics is inherent to the individual, making biometric data a reliable means of verifying identity.

The strength of biometric authentication lies in its reliance on intrinsic traits that are difficult to replicate or forge, unlike the other authentication factors. For example, "something you have" typically refers to possessions like ID cards or mobile devices, while "something you know" pertains to passwords or PINs. "Something you do" might relate to behavioral patterns, such as keystroke dynamics or the way a person interacts with a device, but it is not as commonly recognized as a primary authentication factor like biometrics.

As a result, "something you are" is the correct choice, capturing the essence of biometric authentication’s reliance on physical identity attributes for access control and security.