Which one of the following describes a reference monitor?

A.
Access control concept that refers to an abstract machine that mediates all accesses to objects
by subjects.

B.
Audit concept that refers to monitoring and recording of all accesses to objects by subjects.

C.
Identification concept that refers to the comparison of material supplied by a user with its
reference profile.

D.
Network control concept that distributes the authorization of subject accesses to objects.

Explanation:
A reference monitor is a system component that enforces access controls on an
object. Therefore, the reference monitor concept is an abstract machine that mediates all access
of subjects to objects -Ronald Krutz The CISSP PREP Guide (gold edition) pg 262