Calculate the K_a for an Unknown Monoprotic Acid HX,given That $\times$

Multiple Choice

Calculate the K_a for an unknown monoprotic acid HX,given that a solution of 0.28 M LiX has a pH of 8.90.

A) 2.3 $\times$ 10^-10
B) 3.5 $\times$ 10^-10
C) 1.8 $\times$ 10³
D) 8.9 $\times$ 10^-5
E) 4.4 $\times$ 10^-5