The correct answer is B. pollution.
A mixture of sand, clay, water and bitumen (hydrocarbon) is called tar sands or oil sands. Bitumen is extracted from tar sands and refined it to produce gasoline and extraction of tar sands greatly impact on environment. When gasoline made from tar sands emits more carbon dioxide as compare to traditional oil extraction. The mining of tar sands has increased carbon emissions over a period of time. Thus, increase percentage of carbon dioxide causes pollution.