Which of the following biometric characteristics cannot be used to uniquely authenticate an individual`s identity? 

Answer options:

A. Retina scans
B. Iris scans
C. Palm scans
D. Skin scans

D

The following are typical biometric characteristics that are used to uniquely authenticate an individual`s identity: Fingerprints - Retina scans - Iris scans - Facial scans - Palm scans - Hand geometry - Voice - Handwritten signature dynamics - Source: KRUTZ, Ronald L. & VINES, Russel
D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 39. And: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 4: Access Control (pages 127-131).