An aromatic organic compound [A] on heating with NH3 and Cu2O at high pressure gives [B], The compound [B] on treatment with an ice-cold solution of NaNO2 and HCl gives [C], which on heating with Cu/HCl gives compound [A] again. Identify the compounds [A], [B] and [C]. Write the name of the reaction for the conversion of [B] to [C].