In polythionic acid, ${\mathrm{H}}_2{ \mathrm{S}}_x{\mathrm{O}}_6(x=3$ to $5$) the oxidation state(s) of sulphur is/are:

Given below are two statements: one is labelled as Assertion $\mathrm{A}$ and the other is labelled as Reason $\mathrm{R}$.

Assertion $\mathrm{A}:$ In $\mathrm{T}l{\mathrm{I}}_3,$ isomorphous to ${\mathrm{CsI}}_3$, the metal is present in $+1$ oxidation state.

Reason $\mathrm{R}:$ $\mathrm{T}l$ metal has fourteen $\mathrm{f}$ electrons in its electronic configuration.

In the light of the above statements, choose the most appropriate answer from the options given below: