Number of possible position isomers for dichlorobenzene is 

So the correct answer is B 

As we know, chemical compounds are generated by differences in the arrangement of the atoms that make up the molecule. These substances are referred to as isomers. The structure of the compound given to us has dichloro, i.e., two chlorine atoms are present, and a benzene ring is also present. When the same compound has a different spatial arrangement in space, that is called stereoisomers, whereas isomers that only differ by the position of the substituent group are called positional isomers. The dibromo benzene position isomers are as follows: 

Thus, positional isomers are the identical compounds, but the positions of the substituents linked to the primary group vary. 

photos for SEO Thus, positional isomers are the identical compounds, but the location of the substituents linked to the primary group varies amongst isomeric molecules. 

There for the answer is B