The delocalized cloud of π electrons in benzene is formed by the overlap of 6<u> p-orbitals</u>.
So, option B is correct one.
In the case of hydrocarbons, delocalisation occurs in benzene rings , where a hexagon of six carbon atoms has decalized electrons spread over the whole ring.
All of the carbon atoms in the benzene rings are orbitals around the ring produces a framework of six sigma bonds, while the unhybridized p-orbitals which are perpendicular to this plane over in side-to-side fashion to form three pi-bonds.