What does the class B rating test measure in terms of fire extinguishing capability?

The correct choice highlights that for each 1-B rating in the classification of fire extinguishers, it corresponds to the ability to extinguish a fire involving a specific square footage of flammable liquid. The definition of a class B fire includes those that involve flammable liquids like gasoline, oil, and solvents. The rating system serves to indicate the effectiveness of the extinguisher against these types of fires based on the area it can cover.

In this case, the measurement indicates that each class B rating unit can effectively handle a fire covering one square foot of fuel. Understanding this measurement is crucial for accurately assessing the appropriate fire extinguisher needed based on the size and type of fire that might occur in a given environment. The other options suggest different square footage per 1-B rating, which would misrepresent the capabilities of class B extinguishers, potentially leading to inadequate firefighting resources being selected for a given risk.