Choose the correct option on the $\mathrm{Cl}-\mathrm{O}$ bond length in ${\mathrm{NaClO}}_4$.

All $\mathrm{Cl}-\mathrm{O}$ bonds are of equal length.

Three $\mathrm{Cl}-\mathrm{O}$bonds are of equal length and one longer

All $\mathrm{Cl}-\mathrm{O}$  bond lengths are different

Two $\mathrm{Cl}-\mathrm{O}$ bonds are of same length which are longer compound to other two  $\mathrm{Cl}-\mathrm{O}$bond length.