Final answer:
Aerobic activities, such as cycling, walking, and running, are the most effective exercises for improving cardiorespiratory endurance. They enable sustained, low to moderate exertion, which enhances cardiovascular strength and muscular endurance. Hence, option (a) is correct.
Step-by-step explanation:
The exercises that lead to the greatest improvements in cardiorespiratory endurance are aerobic activities. Aerobic exercise, which involves low to moderate exertion that can be sustained over long periods, causes your heart to beat faster and enables your muscles to use oxygen more efficiently. Regularly engaging in aerobic activities such as cycling, walking, and running builds endurance and makes the heart stronger.
While anaerobic activities like weight training and sprinting improve muscle strength and anaerobic capacity, and flexibility exercises like yoga and Pilates improve the range of motion, aerobic exercises are the most effective at improving cardiorespiratory endurance. Therefore, the correct answer is option (a).