Correct descending order of relative contribution of various greenhouse gases to total global warming is

The correct option is carbon dioxide; methane; CFCs; nitrous oxide.

Greenhouse gases (GHGs) trap heat in the Earth's atmosphere, leading to the greenhouse effect and global warming. The relative contribution of various greenhouse gases to total global warming is determined by both their concentration in the atmosphere and their heat-trapping ability (global warming potential).

According to standard environmental science and IPCC data, the approximate percentage contributions of the major greenhouse gases to global warming are:
1. Carbon dioxide (CO₂): About 60% relative contribution, making it the primary driver of human-induced global warming due to massive emissions from burning fossil fuels and deforestation.
2. Methane (CH₄): About 20% relative contribution, released from agricultural practices, landfills, and fossil fuel extraction.
3. Chlorofluorocarbons (CFCs): About 14% relative contribution, which are synthetic compounds used in refrigeration and aerosol propellants.
4. Nitrous oxide (N₂O): About 6% relative contribution, mainly originating from fertilizer use and agricultural soil management.

Therefore, arranging these greenhouse gases in descending order (highest to lowest contribution) gives:
Carbon dioxide ⇒ Methane ⇒ CFCs ⇒ Nitrous oxide