Water gas is a mixture of

1. carbon monoxide and oxygen
2. carbon monoxide and hydrogen
3. hydrogen and oxygen
4. hydrogen and nitrogen

carbon monoxide and hydrogen

Reason — Water gas is a mixture of carbon monoxide and hydrogen which is produced by passing steam over hot coke at 1000°C.

     $\text{C}+ \text{H}$2 \text{O} \xrightarrow {1000\degree \text{C}} \text({CO + H}2) - \text{Heat}