What Is the Hydronium Ion Concentration of a 0

Multiple Choice

What is the hydronium ion concentration of a 0.500 M acetic acid solution with K_a = 1.8 × 10^-5? The equation for the dissociation of acetic acid is:
CH₃CO₂H(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CH₃CO₂^-(aq) .

A) 3) 0 × 10^-2 M
B) 4) 2 × 10^-2 M
C) 3) 0 × 10^-3 M
D) 4) 2 × 10^-3 M