What is the significance of K_a1 in the context of polyprotic acids?

• A. K_a1 represents the equilibrium constant for the removal of the second acidic hydrogen.
• B. K_a1 represents the equilibrium constant for the addition of the first acidic hydrogen.
• C. K_a1 represents the equilibrium constant for the removal of the third acidic hydrogen.
• D. K_a1 represents the equilibrium constant for the removal of the first acidic hydrogen.

Answer: (D)