The correct answer is B) It offers lasting, effective protection against burn-back. Dry chemical extinguishers are designed to interrupt the chemical reaction of a fire, effectively smothering the flames. This makes them particularly effective against flammable liquid and gas fires, as the dry chemical forms a barrier that prevents the fuel from reigniting or "burning back" after the initial extinguishment. In contrast, carbon dioxide extinguishers work by displacing oxygen, but do not provide the same lasting protection against burn-back. The other options are incorrect because: A) Dry chemical extinguishers do not necessarily have a greater duration than carbon dioxide extinguishers; C) Dry chemicals can be mildly toxic if inhaled in large quantities; and D) Dry chemical extinguishers do not provide a physical heat shield for the operator.