I'm guessing b but I'm not sure
third one, all of the above
the vital capacity of an athlete is higher than a non-athlete because they are trained to do hard work, their lungs get bigger over time and make it easier for them to take long breaths when they are running or doing any other exercise
The circulatory system is system in the human body that provides a network through which our blood flows constantly.The human cardiovascular system is considered closed because there are no holes for blood to enter or leave the system. Correct answer: D
In the closed circulatory system the blood stays confined within the vessels and heart.
