Which of the following is NOT a major greenhouse gas?

• A. Methane
• B. Nitrous oxide
• C. Helium
• D. CFC's

Answer: (C)

Helium is not considered a major greenhouse gas. Greenhouse gases are those that trap heat in the atmosphere and contribute to the greenhouse effect, leading to global warming and climate change. Methane, nitrous oxide, and chlorofluorocarbons (CFCs) are all known for their significant impacts on the greenhouse effect. Methane is emitted during the production and transport of coal, oil, and natural gas, as well as from livestock and other agricultural practices. Nitrous oxide arises from both agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. CFCs, while not prevalent today due to global agreements to phase them out, were once widely used in refrigeration and aerosol propellants and are potent greenhouse gases.

In contrast, helium is a noble gas that does not contribute to the greenhouse effect, as it does not absorb or emit infrared radiation. Its chemical properties lead it to be inert and incapable of participating in the reactions that form greenhouse gases, which makes it fundamentally different from the other gases listed.