I think c? Hydroelectric power reduces pollution, and A, B are irrelevant.
<span> Some examples are the water cycle, the </span>carbon cycle, the phosphorus cycle<span> and the </span><span>nitrogen cycle.
Hope this helps xox :)</span>
Answer is: solution A has 2,57 time greater pH value than solution B.<span>
</span>Concentration of [H⁺] in solution A is than 370x.
pH = -log[H⁺].
pH(solution A) = -log(370x).
pH(solution b) = -log(x).
pH(solution A) / pH(solution B) = -log(370x) / -log(x).
pH(solution A) / pH(solution B) = 2,57.