The nozzle and the eductor must be matched at what gpm to receive the right concentration of foam?

Answer: B — 125 gpm

Foam proportioning relies on Venturi action to draw concentrate into the water stream, and the eductor is calibrated for a specific water flow. When the nozzle delivers the eductor’s rated flow, the amount of concentrate pulled matches the intended ratio, giving the correct foam concentration. If you go above that flow, the eductor can’t pull enough concentrate and the foam becomes diluted; if you go below, the mixture can become too rich or unstable. So, using a nozzle that equals the eductor’s rated GPM ensures the right concentration, which is typically 125 gpm in common setups.