Answer: A
Explanation: The blood–air barrier (alveolar–capillary barrier or membrane) exists in the gas exchanging region of the lungs. It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli. ... The barrier is permeable to molecular oxygen, carbon dioxide, carbon monoxide and many other gases.
Probably 78 but most likely 9
Filtration, coagulation, settling basins and aeration are some examples of water treatment and is denoted as option A.
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What is Filtration?</h3>
This is a technique which is used to separate solids from a liquid or gas substance.
This alongside others mentioned above are used in treating water to remove contaminants and make it safe for drinking and other uses.
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It usually take half lives