Final answer:
After muscular exercise, the blood vessels carrying the lowest concentration of carbon dioxide are the oxygenated arteries in the lower torso.
Step-by-step explanation:
After muscular exercise, the blood vessels carrying the lowest concentration of carbon dioxide are the oxygenated arteries in the lower torso. During exercise, the body requires more oxygen and produces more carbon dioxide as a byproduct. The oxygenated arteries deliver oxygen-rich blood to the muscles, while the deoxygenated veins carry carbon dioxide back to the lungs to be exhaled.