If cindy wanted to increase her endurance by taking supplements or drugs, she would be attempting to increase the
a. uptake of oxygen by red blood cells
b. release of sugars in the blood stream
c. uptake of carbohydrates by the body
d. release of insulin in the body

a. uptake of oxygen by red blood cells

Explanation:

The increase in red blood cells increases the ability of cells to pick up oxygen from the air. This occurs as a consequence of the body's adaptation to prolonged exposure to a given situation. Increasing the number of red blood cells means increasing the ability to carry oxygen through the blood, and thereby improving aerobic performance when the athlete.

If Cindy wanted to increase her resistance by taking supplements or drugs, she would try to increase oxygen uptake by red blood cells and help her metabolism break down the supplement or drug efficiently.

which ever one is showing doing the same exercise in time intervals such as 30 seconds or a minute several times.