The correct answer is bioavailability.
<span>Bioavailability is an important factor in establishing nutrient requirements and it represents the degree to which food nutrients are available for absorption and utilization in the body. The amount of a nutrient in a food that the body can actually use may vary depending on age and physiologic condition.</span>
The answer is <span>The respiratory system supplies the oxygen that the cardiovascular system transports to the different cells for the production of energy.
When air enters the lungs (part of the respiratory system), it passes all way to the alveoli, the smallest functional units of the lung. There, oxygen from the air enters the capillaries, the smallest blood vessels, next to the alveoli. Once in the blood stream, the cardiovascular system transports oxygen to different cells where it is used for the energy production.</span>
I believe it’s your head since it has more friction
