Stress is commonly measured in which of the following units?

Stress is commonly measured in Pounds Per Square Inch (PSI) because this unit accurately represents the amount of force applied to a certain area. In the context of building construction and fire service, understanding stress is crucial because it helps assess how materials will behave under various loads. Stress essentially describes how much internal force a material can withstand before failure, and PSI is a standard unit used in engineering practices to quantify this internal pressure or force per unit area.

The other options do not appropriately measure stress. Square Foot (SF) is a unit of area, not a measure of force or pressure. Kilograms Per Meter (KPM) does not correspond to a recognized unit of stress or force; it's unclear and typically not used in stress measurements in the context of engineering. Pounds Per Second (PPS) is a measure of weight over time, which again does not provide the necessary context for evaluating stress on a material. Thus, PSI is the most relevant unit for stress in building and fire service applications.