Isomer C8H7O2Br on heating with sodalime gives toluene,hence it is an acid.Moreover since it has Degree of unsaturation 5 therefore it is an aromatic carboxylic acid.Since Carboxylic acid on heating gives toluene ,therefore it is having −CH3 group attached to the benzene ring.
Now it forms single isomer on halogenation, therefore −CH3 group must be attached at para position with respect to −COOH group.
Hence correct option is 1.




