A metal M readily forms sulphate MSO4 which is water soluble. It forms oxide MO which becomes inert on heating. It forms insoluble hydroxide which is soluble in NaOH. The metal M is:
The correct option is D Be
Solubility of sulphates of 2nd group elements decreases down the group. BeSO4 and MgSO4 are soluble in water. Only BeO is amphoteric (all other oxides of the group are basic) and thus it dissolves in NaOH.