Final answer:
Cardiorespiratory endurance is the capacity of the heart and lungs to supply oxygen to the muscles during exercise. It is improved through aerobic exercises like running marathons.
Step-by-step explanation:
Cardiorespiratory endurance is best described as the capacity of the heart and lungs to supply oxygen to the muscles during sustained physical activity. It is the ability to engage in prolonged exercise without experiencing fatigue or breathlessness. Aerobic exercises such as running a marathon are examples of activities that improve cardiorespiratory endurance.