The degree of ionization of $\;0.10\;M$ lactic acid is $4.0 \%$

Question

The value of $K_c$ is

(a) $1.66 \times 10^{-5}$

(b) $1.66 \times 10^{-4}$

(c) $1.66 \times 10^{-3}$

(d) $1.66 \times 10^{-2}$