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Here is your answer:
The proper answer to this question is option A "determining point of diminishing returns"! That because the government uses that to get taxes back!
Your answer is A!
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The order of flow of oxygen within the human body may be described simply. Oxygen first is inhaled through the nasal cavity and then passes through the trachea, through the bronchi and into the lungs. In the lungs, the oxygen is passed into the blood stream through the alveoli and then is carried to the heart. The heart pumps this oxygenated blood throughout the body, primarily to organs and muscle cells, where it is consumed in respiration and is converted to carbon dioxide and excreted.
Answer: Serotonin
Explanation:
Serotonin is an hormone, derived from the amino acid, tryptothan. It is involved in vasodilation, sleep regulation, mood changes, capillary permeability, and causes contraction of smooth muscles like that of the stomach to signal hunger.