Answer:
Increased heart rate, during strenuous exercise, helps to regulate the oxygen reaching the tissues.
Step-by-step explanation:
Physical exercise implies an increased effort of the muscles, increasing the energetic demand and the substrate to produce more energy.
Both glucose and oxygen are needed by the muscle tissue during physical exercise, so the increased heart rate ensures the supply of oxygen to that tissue.
Therefore, an increase in heart rate contributes to the regulation of oxygen, whose requirements by the muscles increase with exercise.
Other options are not correct because:
A and C. Water and ammonia regulation is done at the renal level.
D. Regulation of temperature depends on the thermoregulatory center of the nervous system.