An optically inactive hydrocarbon [A] of formula $C_8{H}_{12}$  on reaction with 1 equivalent of $H_2\text{/}Pd$  gives recemic [B] of formula  $C_8{H}_{14}$. [A] reacts with ethylene at  $150°C$ to give and optically inactive hydrocarbon [C] of formula  $C_{10}{H}_{16}$. Reaction of [A] with NBS/light gives [D] with the formula  $C_8{H}_{11}Br$ as a racemic mixture along with an achiral compound. Compound [A] is