`S_(1)`interstitial compound have high melting points, higher than those of pure metals.
`S_(2)` Permanganate titration in presence of hydrochloric acid are unsatisfactory
`S_(3)`: `KmnO_(4)` does not act as an oxidising agent in strong alkaline medium.
`S_(4):KMnO_(4)` On heating in a current of `H_(2)` gives `MnO`

Answer

A

Explanation

`S_1`:Due to strong interatomic forces.
`S_2`:Hydrochloric acid is oxidised to chlorine.
`S_3`:`MnO_4^(-)overset(OH^-)toMnO_4^(2-)`
`S_4:M^(2+)//M (E^(theta)//V)`-negative value decreases across the series.