What term refers to the introduction of new building systems or the extension of existing systems?

The term that refers to the introduction of new building systems or the extension of existing systems is indeed the option that focuses on the specific activities involving building systems. This choice clearly defines the scope of the work being discussed — whether it involves integrating new systems into a building or enhancing already established systems to improve functionality, efficiency, or compliance with current standards.

Building systems can include elements such as HVAC (heating, ventilation, and air conditioning), electrical systems, plumbing, and other mechanical systems that are crucial for the operation and safety of a building. Therefore, recognizing the distinction between simply renovating interiors or making structural adjustments, which do not specifically encapsulate the notion of introducing or extending systems, is essential. The focus is solely on the systems aspect, making the correct choice relevant and precise in describing those activities.