In Gattermann reaction,a diazonium group is replaced by $\underline{X}$ using $\underline{Y}$. $\underline{X}$ and $\underline{Y}$ are:
$\underline{X} \quad \underline{Y}$

• A
  $Cl^{\ominus} \quad Cu / HCl$
• B
  $Cl^{\oplus} \quad CuCl_2 / HCl$
• C
  $Cl^{\ominus} \quad CuCl_2 / HCl$
• D
  $Cl_2 \quad Cu_2 O / HCl$