Correct Response: D. Panting that is observed in some mammals and birds is a feedback response when the internal body temperature rises. Panting increases the evaporation of moisture from the nasal passages, mouth, and throat. Evaporation causes some internal body heat to be lost as it evaporates moisture from the tissues, thus reducing the internal body temperature. Hyperventilation of the lungs (A) is a rapid increase in the volume of air entering the lungs and is a symptom of a more serious condition than overheating. Dilating the capillaries in the mouth and throat (B) is not caused by panting, although it can bring heat up to the surface of the mouth and throat. Panting does not trigger a countercurrent heat exchange (C), in which heat moves from one area to another, even though it enables moisture in the oral cavities to evaporate.
