Citric acid, $H_3C_6H_5O_7(aq)$, is a weak, polyprotic acid that is found in fruits such as oranges and lemons. Citric acid reacts with water, as represented by the following Brønsted-Lowry equations.
$H_3C_6H_5O_7(aq) + H_2O(l) \rightleftharpoons H_2C_6H_5O_7^-(aq) + H_3O^+(aq)$ $K_a = 7.4 \times 10^{-4}$
$H_2C_6H_5O_7^-(aq) + H_2O(l) \rightleftharpoons HC_6H_5O_7^{2-}(aq) + H_3O^+(aq)$ $K_a = 1.7 \times 10^{-5}$
$HC_6H_5O_7^{2-}(aq) + H_2O(l) \rightleftharpoons C_6H_5O_7^{3-}(aq) + H_3O^+(aq)$ $K_a = 4.0 \times 10^{-7}$
The amphiprotic species in the equations above are
A. $H_3C_6H_5O_7(aq)$, $HC_6H_5O_7^{2-}(aq)$, and $H_2O(l)$
B. $H_2C_6H_5O_7^-(aq)$, $HC_6H_5O_7^{2-}(aq)$, and $H_2O(l)$
C. $H_3C_6H_5O_7(aq)$ and $H_2C_6H_5O_7^-(aq)$
D. $HC_6H_5O_7^{2-}(aq)$ and $C_6H_5O_7^{3-}(aq)$
