Observe the following reactions:
$I$. $CO_{(g)} + H_{2(g)} \xrightarrow{X} HCHO_{(g)}$
$II$. $CO_{(g)} + 3 H_{2(g)} \xrightarrow{Y} CH_{4(g)} + H_2O_{(g)}$
The catalysts $X$ and $Y$ in the above reactions are respectively:

• A
  $Cu, Cu$
• B
  $Ni, Ni$
• C
  $Cu, Ni$
• D
  $Ni, Cu$