The $\mathrm { p } K _ { a }$ Of Hydrochloric Acid Is _____, If The

The $\mathrm { p } K _ { a }$ of hydrochloric acid is _____, if the $\mathrm { p } K _ { b }$ of its conjugate base is 8.56 at $25 ^ { \circ } \mathrm { C }$ .

A) 6.78
B) 5.44
C) 4.32
D) 3.56
E) 2.24