Which of the following are meso compounds

a) (2R,3R)-dibromobutane b) (2R,3S)-dibromobutane c) (2R,3S)-3-bromo-2-butanol d) (2R,3R)-3-bromo-2-butanol Answer: b

a) (2R,3R)-dibromobutane b) (2R,3S)-dibromobutane c) (2R,3S)-3-bromo-2-butanol d) (2R,3R)-3-bromo-2-butanol Answer: b