Operational Expenditure (OPEX) includes all ongoing costs required to operate and maintain the data center on a day-to-day basis. These costs are recurring and necessary to keep the facility functioning effectively. Examples of OPEX include staffing costs, service contracts, maintenance materials, consumables, utilities, and recurring software licensing fees. Within EPI's Facilities Management guidance, maintenance activities---such as replacing fans, belts, filters, and other wear-and-tear components---are classic OPEX items because they occur during normal operational cycles, contribute to sustaining facility uptime, and repeat regularly over the equipment lifetime.

However, acquisition of real estate is a capital-intensive investment made once during facility development and falls under Capital Expenditure (CAPEX), not OPEX. CAPEX involves large, long-term investments such as land purchase, building construction, major equipment procurement, or infrastructure upgrades. These expenditures are depreciated over years and do not represent operational overhead.

Therefore, the only option not belonging to OPEX is C -- Acquisition of real estate. Staffing, maintenance material replacement, and annual software licenses are standard OPEX items essential for continuous operation, service delivery, and compliance with operational practices.