Answer:
D. mining
Step-by-step explanation:
The economy of the United States is the largest economy in the world in terms of GDP. United States produces lots of goods and exports more items to other countries.
United States is also famous for mining various natural resources. It is abundant in land resources in terms of metals, minerals and ores. Coal mining is done in the interior coal region, the Appalachian region and the Western coal region. Black Thunder mines and North Antelope Rochelle region in Wyoming are the two largest coal mines in US. Coal mining is one of the main economic activities that occurs in United States.