An athlete with a high count of red blood cells will perform well in tests of physical
endurance because
(a) waste products will be removed from the body easily.
(b) excess levels of glucose will increase levels of respiration.
(c) the reduced plasma volume will lower carbon dioxide levels.
(d) high levels of oxygen will be available to the muscles.
Red blood cells are the carriers of oxygen from the lungs to everywhere else in the body. If there is a high count of red cells in the blood, then high levels of oxygen will be available to the muscles.