<u>Answer:</u>
The Answer is <em><u>Option D. </u></em>
<em>Exchange of respiratory gases, oxygen and carbon dioxide take place in the alveoli of the lungs. Oxygen which is inhaled from the atmosphere diffuses through the walls of the alveoli and reaches to the adjacent capillaries into the red blood cells.</em>
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The answer would be A. carbohydrates (carbs) because carbs are generally composed of sugars and glucose (as an example) has the ratio between carbon, hydrogen and oxygen in a 1:2:1 ratio in its form: C6H12O6
