GKFix MCQ Question

What is the general expression for the second ionization constant of H2X?

• A. Ka2={[H+]^2[X2-]}/[H2X]
• B. Ka2={[H+][X2-]}/[HX-]
• C. Ka2={[H+][HX-]}/[H2X]
• D. Ka2={[X2-]}/[HX-]