The correct answer is B) Ordinary combustible materials where the quenching and cooling effects of quantities of water, or solutions containing large percentages of water, are of first importance. This is correct because a Type A fire involves ordinary combustible materials like wood, paper, cloth, and plastics. For these types of fires, the primary objective is to cool the burning materials and deprive them of oxygen, which is best achieved through the use of large quantities of water or water-based extinguishing agents. The other answer choices are incorrect because they describe different types of fires that require different extinguishing methods. Option A is for electrical fires, option C is for metal fires, and option D is for flammable liquid fires, none of which are the correct classification for a Type A fire.