One greenhouse gas contributes 14% to total global warming and another contributes 6%. These are respectively identified as

N2O and CO2
CFCs and N2O
Methane and CO2
Methane and CFCs E. CFCs and CO2

The correct answer is: C. Methane and CO2.

Methane is a greenhouse gas that contributes 14% to total global warming. It is a colorless, odorless gas that is produced by the decomposition of organic matter. Methane is also released from natural gas and oil production, as well as from landfills and agriculture.

Carbon dioxide is a greenhouse gas that contributes 6% to total global warming. It is a colorless, odorless gas that is produced when fossil fuels are burned. Carbon dioxide is also released from natural processes, such as respiration and volcanic eruptions.

CFCs are chlorofluorocarbons. They are greenhouse gases that were once widely used in refrigerants and aerosol propellants. However, CFCs were banned in the 1980s because they were found to be damaging to the ozone layer.

The other options are incorrect because they do not accurately reflect the contribution of each greenhouse gas to total global warming.