Which of the following will oxidise $\mathrm{Mn}{}^{2+}$ to $\mathrm{MnO}{}_4{}^{-}$ in acidic solution?

The $+5$ state of bismuth is destabilised by the inert pair effect, so bismuthate is a very strong oxidant and converts $\mathrm{Mn}{}^{2+}$ to purple permanganate. Phosphate and sulfate contain P(V) and S(VI) in stable states with no oxidising tendency in this sense.