Consider the K_a Values for the Following Acids

Consider the K_a values for the following acids:
Cyanic acid,HOCN,3.5 × 10^-4
Formic acid,HCHO₂,1.7 × 10^-4
Lactic acid,HC₃H₅O₃,1.3 × 10^-4
Propionic acid,HC₃H₅O₂,1.3 × 10^-5
Benzoic acid,HC₇H₅O₂,6.3 × 10^-5
Which has the strongest conjugate base?

A) propionic acid
B) benzoic acid
C) lactic acid
D) formic acid
E) cyanic