Consider the stereochemical outcome of additions to alkenes.

Both $\mathrm{Br_2}$ addition (through a bromonium ion that is opened by backside attack) and the $\mathrm{KMnO_4}$/$\mathrm{OsO_4}$ route should be analysed by their stereospecificity. (A) Anti addition of $\mathrm{Br_2}$ to the trans (E) alkene gives the (2R,3S) product, which has an internal mirror plane, hence meso: correct. (B) Anti addition to the cis (Z) alkene gives the (2R,3R) and (2S,3S) pair, a racemic mixture, not a meso compound: wrong. (C) Cold alkaline permanganate adds two OH groups on the same face (syn addition) through a cyclic manganate ester; syn addition to the cis alkene gives the (2R,3S) meso-diol: correct (the same reagent on the E alkene would give the racemic diol). (D) In bromine water the bromonium ion is opened by $\mathrm{H_2O}$ from the face opposite to bromine, so the Br and OH are trans on the ring, not cis: wrong. (2,3-Dibromobutane has exactly three stereoisomers: the (R,R)/(S,S) pair and one meso form.)