Final answer:
The X-Server is responsible for providing the Monitor and Control Workstation operator with an X-Windows terminal display.
Step-by-step explanation:
The element that provides the Monitor and Control Workstation (MCW) operator with an X-Windows terminal displayed at the MCW is the b) X-Server. The X-Server is responsible for managing the display and handling the input/output requests from the X-Windows clients. Hence, in the context of this question, the X-Server acts as a service providing the graphical interface to the users.