The reaction in which dihydrogen $(H_2)$ acts as an oxidising agent is:

• A
  $Pd^{2+}_{(aq)} + H_{2(g)} \longrightarrow Pd_{(s)} + 2H^+_{(aq)}$
• B
  $CuO_{(s)} + H_{2(g)} \longrightarrow Cu_{(s)} + H_2O_{(g)}$
• C
  $2Na_{(s)} + H_{2(g)} \longrightarrow 2NaH_{(s)}$
• D
  $O_{2(g)} + 2H_{2(g)} \longrightarrow 2H_2O_{(l)}$