9. 0.30M in NaF以及0.46 M in HF溶液中,氫離子[H+]濃度為何? (Ka = 7.2 × 10–4 ) (A) 1.2 × 10–4 M (B) 5.7 × 10–3 M (C) 231.5 × 10–2 M (D) 4.7 × 10–4 M