Which of the following is a major greenhouse gas?

• A. Ozone (O3)
• B. Carbon dioxide (CO2)
• C. Helium (He)
• D. Argon (Ar)

Answer: (B)

Carbon dioxide (CO2) is a major greenhouse gas due to its significant role in trapping heat in the Earth's atmosphere. It is produced primarily through human activities such as burning fossil fuels, deforestation, and industrial processes. Once emitted, CO2 can remain in the atmosphere for hundreds of years, contributing to the greenhouse effect, which leads to global warming and climate change.

Greenhouse gases like CO2 absorb infrared radiation, preventing it from escaping into space, and this effect warms the planet. While ozone (O3) does act as a greenhouse gas, its impact is more localized to the stratosphere, where it protects the Earth from harmful UV radiation rather than significantly contributing to global warming in the same way that carbon dioxide does. Helium and argon, on the other hand, are noble gases that do not contribute to the greenhouse effect, as they do not absorb infrared radiation and are relatively inert in environmental processes.