IT infrastructure comprises the core technological components required to operate and manage enterprise IT environments. It is fundamentally composed of three main categories: hardware, software, and networking. Networking is a critical component that includes hardware like routers, switches, and cables, as well as software that enables communication and connectivity between computers, servers, and other devices. This connectivity is essential for data sharing, resource access, and the overall functioning of all information systems built upon the infrastructure.

A. Data: Data is the information that is stored, processed, and transmitted by the IT infrastructure, not a structural component of the infrastructure itself.

B. People: People are the users, operators, and managers of the IT system; they are a crucial part of the socio-technical system but not a component of the technology infrastructure.

D. Printer: A printer is a peripheral or endpoint device. While it connects to and utilizes the network, it is considered a device supported by the infrastructure, not a foundational component of it.

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1. Vendor Documentation: IBM Technology. (n.d.). What is IT infrastructure? IBM. Retrieved from https://www.ibm.com/topics/it-infrastructure. In the section "What are the components of IT infrastructure?", IBM explicitly lists "networking components (including switches, routers and hubs)" as a key part of the hardware infrastructure.

2. University Courseware: Laudon, K. C., & Laudon, J. P. (2011). Essentials of management information systems (9th ed.). Pearson. As used in course materials for information systems management, Chapter 5, "IT Infrastructure and Emerging Technologies," defines IT infrastructure as consisting of a set of physical devices and software applications, explicitly identifying "Networking/telecommunications platforms" as one of the seven major components (p. 137, Figure 5-2).

3. Peer-Reviewed Academic Publication: Broadbent, M., & Weill, P. (1997). Management by Maxim: How Business and IT Managers Can Create IT Infrastructures. Sloan Management Review, 38(3), 1-14. This foundational paper on IT infrastructure defines it as the base foundation of budgeted-for IT capability, which includes "communication technologies" (networks) as a core service and component (p. 4).