A is not optically active because when it goes through the bromination reaction, it does not produce any chiral centers. one bromine is attached to a CH2, the other is attached to a carbon attached to 2 other CH2s (Br - C(CH2)).
B is not the answer either because it only has one chiral center, thus leading to only one enantiomer. diastereomers usually have two chiral centers that have different configurations.