Final answer:
In the context of the Fitwel building rating system, the habitual users within a project boundary are referred to as 'Regular occupants'. These individuals are the primary focus of health-centered design and operational strategies to promote their well-being.
Step-by-step explanation:
The number of habitual users within the project boundary of a building or space where Fitwel Strategies will be applied is called A) Regular occupants. Fitwel is a building rating system that provides guidelines on how to design and operate healthier buildings. The term 'Regular occupants' refers to individuals who are expected to regularly use or inhabit a given space, such as employees in an office building. These individuals are the primary focus of Fitwel Strategies, as the goal is to ensure their health and well-being through various building design and operational strategies.