A toxic compound ‘A’ when reacted with \( \mathrm{NaCN} \) in aqueous acidic medium yields an edible cooking component and food preservative ‘'B’'. '‘B’' is converted to '‘C’' by diborane and can be used as an additive to petrol to reduce emission. ‘'C’' upon reaction with oleum at \( 140^\circ \mathrm{C} \) yields an inhalable anesthetic '‘D’'. Identify ‘'A'’, '‘B’', '‘C'’ & '‘D’', respectively:
