In the solid state, $PCl_{5}$ exists as

• A
  $[PCl_{4}]^{-}$ and $[PCl_{6}]^{+}$ ions
• B
  covalent $PCl_{5}$ molecules only
• C
  $[PCl_{4}]^{+}$ and $[PCl_{6}]^{-}$ ions
• D
  covalent $P_{2}Cl_{10}$ molecules only