Among the options provided, B. Natural gas is generally considered the least polluting fossil fuel.
Natural gas emits fewer greenhouse gases compared to coal and petroleum (oil) when burned for energy. It produces lower levels of carbon dioxide (CO2), sulfur dioxide (SO2), and particulates, making it a cleaner-burning option.
Coal is the dirtiest among the three, as it releases the highest amounts of CO2 and other pollutants when combusted. Petroleum is also more polluting than natural gas, though less so than coal.
So, in terms of pollution, the order from least to most polluting would be: Natural gas < Petroleum < Coal.