These are possible answer:
Only aproximately 3% of earth's water is drinkable. (C.)
Water comprises the majority of all living organisms. (D.)
Why are A. and B. wrong?:
70% to 71% of Earth's surface is covered by water, not 75%
Water can be reused, that is the function of the suage and water treatment stations, to make the decreasing amount of fresh water we have, reusable.
Hope it helped,
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