The correct option is C Decreases to −1 w.r.t NaBr and increases to +1 w.r.t NaBrO
The oxidation number of bromine in Br2,NaBr and NaBrO is 0,−1 and +1 respectively.
Hence, during the reaction, the oxidation number of bromine in Br2 decreases to −1 w.r.t NaBr and increases to +1 w.r.t NaBrO.
Thus, the correct option will be C.