Which Equation Is NOT Required to Determine the PH of 0.10

Which equation is NOT required to determine the pH of 0.10 M solution of weak acid,HA?

A) HA + H₂O ⇋ A⁻ + H₃O⁺ K_a = 2.4 × 10⁻⁶
B) H₂O + H₂O ⇋ H₃O⁺ + OH⁻ K_w = 1 × 10⁻¹⁴
C) 0) 10 = [HA] + [A⁻]
D) [H₃O⁺] = [OH⁻] + [A⁻]
E) A⁻ + H₂O ⇋ HA + OH⁻ K_b = 4.2 × 10⁻⁹