Carlos is a college soccer player. To assess his current aerobic capacity, the lab technician will have him run on a graded treadmill while measurements are taken. What specific physiological quantity will this test primarily measure?

• A. the electrical activity of his heart during maximal exertion
• B. the maximum volume of oxygen his muscles consume per minute
• C. the total volume of air his lungs can hold after training
• D.  the number of breaths he takes per minute while fatigued