Final answer:
Mowing the lawn (Option C) is considered aerobic exercise because it involves sustained physical activity that helps build endurance and strengthens the heart.
Step-by-step explanation:
Of the activities listed, C. mowing the lawn might be considered aerobic exercise. Aerobic exercise is a physical activity that usually involves moderate intensity and is sustained over a period of time to increase cardiovascular endurance. Activities like surfing the web (A), taking a catnap (B), and paying bills (D) do not meet the criteria for aerobic exercise as they do not significantly elevate the heart rate nor involve prolonged physical activity.
Regularly done aerobic activities help build up endurance and strengthen the heart. Therefore, mowing the lawn, which involves sustained physical activity and uses a good amount of energy, fits into this category. Other household chores or activities may also be aerobic if they are done at a sufficient intensity and for a long enough duration.