19. 25℃ 時,某水溶液中 [H⁺]/[OH⁻] = 25,則其 pH 值 = ? (log2 = 0.301, log3 = 0.477) (A) 5.3(B) 5.7 (C) 6.3 (D) 6.7 (E) 7.2