Which of the Following Equations Would Be Appropriate for Calculating $\rightarrow$

Which of the following equations would be appropriate for calculating the change in the freezing point of an aqueous NaHSO₄ solution? (NaHSO₄ dissociates in solution in a two-step process.)

NaHSO₄(s) $\rightarrow$ Na⁺(aq) + HSO₄^-(aq)   (100% dissociation)
HSO₄^-(aq) $\rightarrow$ H⁺(aq) + SO₄^2-(aq)   (10% dissociation)

A) T_FP = (1 + 0.10) k_fm
B) T_FP = (0.10) k_fm
C) T_FP = [1 + 2( 0.10) ]k_fm
D) T_FP = (0.20) k_fm
E) T_FP = (2 + 0.10) k_fm