I believe the correct answer is B. One advantage of conventional natural gas as an energy resource is its lower carbon dioxide emissions as compared with the use of coal. Natural gas is considered as the cleanest fossil fuel and the most efficient source of energy. It contains less impurities as compared to other energy sources and is less complex chemically resulting to lesser emissions of CO2, CO and nitrous oxides which contributes to air pollution. Natural gas consists of methane primarily, higher alkanes and traces of carbon dioxide hydrogen sulfide, nitrogen and helium. This is formed from a number of process for a million of years ago from decaying plants and animals