Which is the strongest acid in the following?

Among all $\left({\mathrm{HClO}}_{3^{\mathrm{\prime }}}{\mathrm{HClO}}_{4^{\mathrm{\prime }}}{\mathrm{H}}_2{\mathrm{SO}}_{3^{\mathrm{\prime }}}\text{ and }{\mathrm{H}}_2{\mathrm{SO}}_4\right)$ ${\mathrm{HClO}}_4$ is the strongest acid. This is because the conjugate base ClO₄ – ion is stabilised by 4 equivalent resonance structures, i.e.,${\mathrm{ClO}}_4^{-}$ is the weakest conjugate base.
Order of acidic strength:
${\mathrm{HClO}}_4>{\mathrm{HClO}}_3>{\mathrm{H}}_2{\mathrm{SO}}_4>{\mathrm{H}}_2{\mathrm{SO}}_3$
For oxyacids of different elements:
Acidity strength α Electronegativity of central atom For different oxyacids of same elements:
Acidic strength α Oxidation state of element