While Reviewing the Wireless Router, the Systems Administrator of a Small

While reviewing the wireless router, the systems administrator of a small business determines someone is spoofing the MAC address of an authorized device. Given the table below: Which of the following should be the administrator's NEXT step to detect if there is a rogue system without impacting availability?

A) Conduct a ping sweep.
B) Physically check each system.
C) Deny Internet access to the "UNKNOWN" hostname.
D) Apply MAC filtering.