Which atmospheric component does NOT contribute to global warming?

The answer is C, nitrogen (N₂). Nitrogen makes up about 78% of the Earth's atmosphere and is a relatively inert gas. It does not absorb infrared radiation, which is a key mechanism for warming the atmosphere.

In contrast, carbon dioxide (CO₂), methane (CH₄), and water vapor (H₂O) are all greenhouse gases. These gases are capable of trapping heat within the atmosphere by absorbing and re-emitting infrared radiation. CO₂ is produced from various natural processes and human activities, and it has a significant impact on the greenhouse effect. Methane is even more effective at trapping heat, though it is present in smaller quantities compared to CO₂. Water vapor, while not directly anthropogenic, increases in concentration as the Earth's temperature rises, enhancing the greenhouse effect.

Thus, nitrogen does not contribute to global warming due to its inert properties, making it the correct answer to the question.