Which variable of the operational environment describes the structures and systems that support the population?

The correct choice identifies "Infrastructure" as the variable of the operational environment that describes the structures and systems supporting the population. Infrastructure encompasses essential components such as transportation networks, utilities, communication systems, and services that facilitate daily life and economic activity. These elements are critical for the stability and functionality of communities, providing the necessary support for effective governance, security, and social well-being.

Understanding the infrastructure's role is vital in military planning and operations, as it directly affects how forces can operate within a given area. By recognizing the physical and systemic foundations that underlie civilian life, military planners can better assess how to engage with the population, sustain it during operations, and optimize their tactical and operational objectives. Infrastructure also plays a significant role in enabling or constraining access and logistics for any military campaign.