Which of the following is the water-gas shift reaction?

• A
  $C_{(s)} + H_2O_{(g)} \xrightarrow{1270 \ K} CO_{(g)} + H_{2(g)}$
• B
  $CH_{4(g)} + H_2O_{(g)} \xrightarrow{1270 \ K} CO_{(g)} + 3H_{2(g)}$
• C
  $CO_{(g)} + H_2O_{(g)} \xrightarrow[\text{iron chromate}]{673 \ K} CO_{2(g)} + H_{2(g)}$
• D
  $2H_2O_{(l)} \xrightarrow{\text{electrolysis}} 2H_{2(g)} + O_{2(g)}$