Which of the following devices is most likely to be in the same level as...

In the Purdue model, HMIs typically reside at Level 2 (Supervisory Control), providing interfaces for operators to monitor and control devices. Remote Terminal Units (RTUs) (D) also commonly reside at this level, interfacing between controllers and supervisory systems.

Variable speed drives (A) and PLCs (B) are usually located at Level 1 (Control Devices LAN).

Data historians (C) typically reside at Level 3 or higher in the Operations Support DMZ or enterprise network.

GICSP materials emphasize proper classification of devices by Purdue levels for effective network segmentation and security.