Which of the following is an example of a biometric identifier?

A biometric identifier is a unique physical characteristic or behavioral trait that can be used to verify an individual's identity. Fingerprint recognition is a perfect example of this, as it relies on the unique patterns found in an individual's fingerprints to authenticate their identity. This method is highly secure because each person's fingerprints are distinct, making it difficult for someone to replicate or guess.

In contrast, password complexity, security questions, and PIN codes are all forms of knowledge-based authentication. They depend on what a person knows rather than who they are. These methods can be more susceptible to social engineering attacks or may be forgotten, leading to lockouts or security vulnerabilities. By utilizing a biometric identifier like fingerprint recognition, the security system leverages a physical trait that is inherent to an individual, providing a more robust and reliable means of authentication.