Find the Correct Equilibrium Constant That Shows the Ionization Constant $\frac{[\mathrm{HA}]}{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\left[\mathrm{A}^{-}\right]}$

Multiple Choice

Find the correct equilibrium constant that shows the ionization constant of a weak acid HA.

A) K_a = $\frac{[\mathrm{HA}]}{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\left[\mathrm{A}^{-}\right]}$
B) K_a = $\frac { \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] \left[ \mathrm { A } ^ { - } \right] } { [ \mathrm { HA } ] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] }$
C) K_a = $\frac { \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] \left[ \mathrm { A } ^ { - } \right] } { [ \mathrm { HA } ] }$
D) K_a = $\frac { [ \mathrm { HA } ] \left[ \mathrm { H } _ { 2 } \mathrm { O } \right] } { \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] \left[ \mathrm { A } ^ { - } \right] }$
E) K_a = $\frac{\left[\mathrm{A}^{-}\right]}{[\mathrm{HA}]}$