Which gas is produced when a metal reacts with water? A. oxygen B. nitrogen C. chlorine D. hydrogen

The correct answer is D. Hydrogen.

When a metal reacts with water, the metal atoms displace the hydrogen atoms in the water molecules. This produces hydrogen gas and a metal hydroxide. The reaction is as follows:

$2 \text{Na} + 2 \text{H}_2\text{O} \to 2 \text{NaOH} + \text{H}_2$

Oxygen is not produced in this reaction. Nitrogen and chlorine are not elements that are typically found in water.