Which of the following has least tendency to liberate $$\mathrm{H}_{2}$$ from mineral acids?

In neutral or alkaline solution, $$\mathrm{MnO}_{4}^{-}$$ oxidises thiosulphate to :

Given below are two statements.

Statement I : Iron (III) catalyst, acidified $$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$$ and neutral $$\mathrm{KMnO}_{4}$$ have the ability to oxidise $$\mathrm{I}^{-}$$ to $$\mathrm{I}_{2}$$ independently.

Statement II : Manganate ion is paramagnetic in nature and involves $$\mathrm{p} \pi-\mathrm{p} \pi$$ bonding.

In the light of the above statements, choose the correct answer from the options given below.

The total number of $$\mathrm{Mn}=\mathrm{O}$$ bonds in $$\mathrm{Mn}_{2} \mathrm{O}_{7}$$ is __________.