Concept:Global warming is mainly caused by greenhouse gases that trap heat in the atmosphere.
Explanation:Carbon dioxide,
CO2, is a major greenhouse gas.
It is released when fossil fuels are burned.
CO2 absorbs heat radiating from the Earth's surface and prevents it from escaping into space.
This trapped heat increases the planet's temperature, leading to global warming.
The other gases listed,
O2,
N2, and He, do not significantly trap heat.
Therefore, the gas responsible for global warming among the options is carbon dioxide.
Answer:B.
CO2