How is a fingerprint defined?

A fingerprint is defined as a reproduction of the skin pattern on a finger or thumb. This definition emphasizes that fingerprints are unique patterns created by the arrangement of ridges and lines on the skin's surface. These patterns serve as critical identifiers, as no two individuals have the same fingerprint, making them a vital tool in forensic science and law enforcement for identity verification.

The emphasis on reproduction highlights that fingerprints can be recorded and examined in various ways, including ink impressions or digital scans. Other options do not accurately describe what a fingerprint fundamentally is; for instance, a full hand impression involves more than just a finger or thumb, while a digital record relates to technology and identity management rather than the physical characteristic itself. Lastly, a blood type sample references a completely different biological marker unrelated to skin patterns. Therefore, the focus on the unique skin pattern is what establishes option B as the correct definition of a fingerprint.