Which of the following is a Gattermann reaction?

• A
  $ArN_{2}^{+}X^{-} \xrightarrow{Cu/HCl} ArCl + N_{2} \uparrow$
• B
  $ArN_{2}^{+}X^{-}$ $\xrightarrow{HBF_{4}} ArN_{2}^{+}BF_{4}^{-}$ $\xrightarrow{\Delta} ArF + N_{2} \uparrow + BF_{3}$
• C
  $ArN_{2}^{+}X^{-} \xrightarrow{Cu/HBr} ArBr + N_{2} \uparrow$
• D
  $ArN_{2}^{+}X^{-} \xrightarrow{KI, \Delta} ArI + N_{2} \uparrow + KX$