The correct option is Methane.
Explanation
Greenhouse gases (GHGs) are components of the atmosphere that absorb and emit radiant energy within the thermal infrared range. This process traps heat and causes the greenhouse effect. The ability of a gas to contribute to global warming depends on its radiative efficiency and its lifetime in the atmosphere.
Option Analysis:
- Methane is Correct: Methane ($CH_4$) is a major greenhouse gas. It is emitted during the production and transport of coal, oil, and natural gas, as well as by livestock and other agricultural practices. Although its concentration in the atmosphere is lower than that of Carbon Dioxide ($CO_2$), it is significantly more potent at trapping heat in the short term.
- Oxygen is Incorrect: Oxygen ($O_2$) is a homonuclear diatomic molecule. It does not absorb infrared radiation because its electric dipole moment does not change during vibration. Therefore, it does not contribute to the greenhouse effect.
- Neon is Incorrect: Neon ($Ne$) is a noble gas. It is chemically inert and transparent to infrared radiation, meaning it does not trap heat in the atmosphere.
- Helium is Incorrect: Helium ($He$) is also a noble gas and does not interact with infrared radiation to cause warming.
Key Takeaway: The primary greenhouse gases in Earth's atmosphere are Water Vapor ($H_2O$), Carbon Dioxide ($CO_2$), Methane ($CH_4$), Nitrous Oxide ($N_2O$), and Ozone ($O_3$). Major atmospheric components like Nitrogen ($N_2$) and Oxygen ($O_2$) are not greenhouse gases.