Finished foam is defined as:

• A. Foam concentrate that combines fluoroprotein with aqueous film forming foam.
• B. Completed product after air is introduced into the foam solution.
• C. Foam solution that exists between the proportioner and the nozzle.
• D. The process of aerating the foam solution to create finished foam.

Answer: (B)

Finished foam is the completed foam product after air is added to the foam solution. In foam firefighting, you mix foam concentrate with water to make a foam solution, then introduce air through the system to create bubbles and a stable foam blanket. That aerated product—the finished foam—is what blankets the fire and provides cooling and fuel separation.

The other statements describe either the concentrate itself, the foam solution before aeration, or the act of aerating itself, not the final foam product.