Which of the Following Expressions for K Is Correct for the Reaction

Which of the following expressions for K is correct for the reaction given below?
HF(aq) + H₂O( $\ell$ ) $\rightleftharpoons$ F^-(aq) + H₃O⁺(aq)

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