Select the solution below that will have the lowest pH.

A list of K_a/K_b values is provided.

K_a of HOAc = 1.8 x 10^-5

K_a of HClO = 3.2 x 10^-8

K_b of HS^- = 1.8 x 10^-7

K_b of NH₃ = 1.8 x 10^-5

K_a of HCN = 4.00 x 10^-10

K_a of HN₃ = 1.9 x 10^-5

K_b of C₆H₅O^- = 6.25 x 10^-5

K_a of HNO₂ = 4.0 x 10^-4