GKFix MCQ Question

What is the expression for the first ionization constant (Ka1) of a dibasic acid H2X?

• A. Ka1 = [H+][X^2–]/[H2X]
• B. Ka1 = [H+][HX–]/[H2X]
• C. Ka1 = [H+][HX–]/[X^2–]
• D. Ka1 = [H+][H2X]/[HX–]