in which of the following d orbitals are not used in central atom in hybridisation ? 
a) PF5 (s)    b) PCl5(l)    c)Pbr5(s)   d)Xef6(s)

PBr5(s) does not involve d-orbital involved in hybridisation. PBr5 exists as [PBr4]+ and Br-. [PBr4]+ has so3 hybridisation. All other compounds have d- orbital in their given state.