Which of the following gases is nonflammable and does not support life?

The correct answer identifies a characteristic of both nitric oxide and carbon dioxide regarding their nonflammable nature and their respective roles in supporting life.

Nitric oxide, while used in medical applications, is not a flammable gas, and it functions as a signaling molecule in the body rather than an essential gas for sustaining life in the way oxygen does. While it plays important roles in various biological processes, it does not contribute to respiration.

Carbon dioxide, on the other hand, is also nonflammable and is a byproduct of respiration in living organisms. Although it is vital in certain physiological processes, in high concentrations it becomes toxic and does not support life in the same way oxygen does. In fact, an excess of carbon dioxide can lead to asphyxiation and is harmful to living organisms when present in significant amounts.

In summary, both gases are nonflammable and do not support life in a direct manner, making the option reflecting that both options fulfill the criteria the most accurate choice.