GKFix MCQ Question

What is the general expression for Ka1 of a diprotic acid H₂A?

• A. Ka1 = [H⁺][A²⁻]/[HA⁻]
• B. Ka1 = [H⁺]²[A²⁻]/[H₂A]
• C. Ka1 = [HA⁻]/[H₂A]
• D. Ka1 = [H⁺][HA⁻]/[H₂A]