Answer :
External respiration is the process of diffusion in lungs. It is indicated in bold. The rest is internal respiration i.e diffusion of oxygen within tissues
Breathing both inside and outside To provide us energy, our lungs deliver oxygen from the outside air to the cells through the blood and circulatory system. Oxygen diffuses into the blood as we breathe in, entering the lungs. It is pumped into the cells after being delivered to the heart. The carbon dioxide waste that results from the body's cells breaking down carbohydrates diffuses into the blood, then diffuses from the blood into the lungs where it is released when breathing out. Exchange of one gas (oxygen) for another (carbon dioxide). Both the lungs (external respiration) and the cells participate in this gas exchange (internal respiration).
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