Answer
Please see the work below.
Work Step by Step
We know that the conjugate acid of a base is a species which is different from the base only by one $H^+$.Let us consider base $HSO_3^-$ then we have its conjugate as $H_2SO_3$ and not $H_2SO_4$. $H_2SO_4$ and $HSO_3^-$ have only one H and one O difference.