Of the following, which BEST provides non- repudiation with regards to access to a server...

Biometric readers are the best option to provide non-repudiation with regards to access to a server room. Non-repudiation is the ability to prove that an action or event occurred and was performed by a specific entity. Biometric readers use physical characteristics such as fingerprints, iris patterns, or facial features to authenticate users, and they are hard to forge or share. Therefore, they can provide strong evidence of who accessed the server room and when. The other options are not as effective in providing non-repudiation, as they can be lost, stolen, copied, or shared by users. Fobs and PINs are examples of something you have and something you know, respectively. Locked and secured cages are physical barriers that can be bypassed by unauthorized persons. Proximity readers are devices that detect the presence of a nearby object, such as a card or a tag, and grant access accordingly. References: Official (ISC)2 CISSP CBK Reference, Fifth Edition, Domain 5: Identity and Access Management, p. 615-616; CISSP All-in-One Exam Guide, Eighth Edition, Chapter 5: Identity and Access Management, p. 321-322.