The correct answer is D) breaks up and cools the fire. The main advantage of a steady stream of water on a class "A" fire is that it breaks up the solid combustible materials and cools them, effectively extinguishing the fire. Water acts as a heat sink, absorbing the heat from the fire and reducing the temperature to the point where combustion can no longer be sustained. This cooling effect is the primary mechanism by which water effectively puts out class "A" fires, which involve ordinary combustible materials such as wood, paper, or fabrics. The other answer choices are incorrect because: A) simply washing the fire away does not address the underlying heat source, B) removing the oxygen is more applicable to class "B" (flammable liquid) fires, and C) while protecting the firefighting crew is important, it is not the main advantage of using a water stream on a class "A" fire.