Answer:
Brisk walking.
Explanation:
Exercises that help to improve cardiorespiratory health are aerobic ones, because this type involves oxygen as a principal source of energy, which requires to breath well. Aerobic exercises are long but low intensity because don't require weightlifting or related. Actually aerobic means "with oxygen".
In this case, brisk walking is the right answer because is an aerobic activity which is centered in oxygen, which will help to improve cardiorespiratory system. The counterpart of this exercise is anaerobic which is without oxygen, these are high intensity and pressure exercise like weightlifting.
