A hiker experiences a drop in blood oxygen concentration as he climbs a mountain. Which response would be best classified as homeostatic? * The hiker's heart rate decreases in order to lower his oxygen requirements. The hiker's breathing rate increases in order to raise his blood oxygen concentration. The hiker's heart rate increases in order to expel more carbon dioxide from the lungs. The hiker's breathing rate decreases in order to conserve oxygen in the blood.