Final answer:
The chemoreceptors in the aortic and carotid bodies send input to the respiratory center via the dorsal respiratory group (DRG) in the medulla oblongata.
Step-by-step explanation:
The correct answer is A. Dorsal respiratory group.
The chemoreceptors located in the aortic and carotid bodies send input to the respiratory center via the dorsal respiratory group (DRG). The DRG, located in the medulla oblongata, is responsible for maintaining a constant breathing rhythm by stimulating the diaphragm and intercostal muscles to contract for inspiration. The input from the chemoreceptors helps regulate and adjust the respiratory rate and depth based on the levels of oxygen, carbon dioxide, and pH in the blood.