Iron $(III)$ catalyses the reaction between iodide and persulphate ions,in which
$A$. $Fe^{3+}$ oxidises the iodide ion
$B$. $Fe^{3+}$ oxidises the persulphate ion
$C$. $Fe^{2+}$ reduces the iodide ion
$D$. $Fe^{2+}$ reduces the persulphate ion
Choose the most appropriate answer from the options given below:

• A
  $B$ and $C$ only
• B
  $B$ only
• C
  $A$ only
• D
  $A$ and $D$ only