When zeolite (Hydrated sodium aluminium silicate) is treated with hard water the sodium ions are exchanged with

• A

  ${\mathrm{OH}}^{-} \mathrm{ions}$

• B

  ${\mathrm{SO}}_4^{2-} \mathrm{ions}$

• C

  ${\mathrm{Ca}}^{2+} \mathrm{ions}$

• D

  ${\mathrm{H}}^{+} \mathrm{ions}$