The order of stability of the following carbocations :

Compound $$\left( A \right),\,{C_8}{H_9}Br,\,\,\,$$ gives a white precipitate when warmed with alcoholic $$AgN{O_3}.$$ Oxidation of $$(A)$$ gives an acid $$\left( B \right),$$ $${C_8}{H_6}{O_4}.\,\,\left( B \right)$$ easily forms anhydride on heating. Identify the compound $$(A).$$

A compound with molecular mass 180 is acylated with CH₃COCl to get a compound with molecular mass 390. The number of amino groups present per molecule of the former compound is:

The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was: