An aqueous solution of sodium carbonate has a pH greater than 7 because

• A

  It contains more carbonate ions than ${\mathrm{H}}_2\mathrm{O}$ molecules

• B

  It contains more hydroxide ions than carbonate ions

• C

  ${\mathrm{Na}}^{+}$ ions react with water

• D

  Carbonate ions react with${\mathrm{Na}}^{+}$