The number of pi electrons in benzene is 

• $\mathrm{\pi }$ bond: a link that is created when the p orbitals of two nearby atoms cross, perpendicular to any sigma bonds that may also exist between the same atoms. $6-\mathrm{\pi }$ electrons result from the $3-\mathrm{\pi }$bonds with benzene. 

Hence option(B) 6 is correct.