In solid state PCl5 is a :
In solid state PCl5 tries to exist as oppositely charged ions like
(1) PCl+4 and (2) PCl−6 as the ionic bonding enhances the crystalline nature .
also PCl+4 is tetrahedral , while PCl−6 is octahedral . these structure fit well into each other which gives more stability to solid structure .
Hence option D is correct.