D

The United States is rich in natural resources.In addition to its plentiful water resources，it is also blessed with dense forests and abundant mineral resources.

The eastern half and the west coast of today’s United States used to be covered with large dense forests;however，many of these have disappeared owing to agricultural and urban growth as well as logging.About 25％ of the nation’s land is still covered with forests，but only about 10％ of the original virgin forests remain，mostly in the west where some of the trees are as much as 3，000 years old.Forests have been useful in helping to prevent soil erosion，and in providing wood as a raw material for American industry.

The United States also has rich mineral resources，most of which are found in the western states.The principal energy resources are coal，oil，and gas.Most of the coal reserves are found in the Appalachians，the Central Plain and the Rockies.Coal is now mainly used to generate electricity and make steel.It provides about 22％ of all the energy used by Americans each year.

Most of the energy consumed in the United States is from oil and natural gas，with oil providing about 39％ and gas 24％ of the total.Most of America’s oil reserves are in Texas，Louisiana，Oklahoma and Alaska.The United States was once the leading oil producer in the world，but it currently has to import about half of the amount it needs as it uses far more than any other country.It also imports natural gas from Canada in addition to producing about 23％ of the world’s gas.

The United States also has large reserves of metals such as gold，silver，lead and zinc.High quality iron ore suitable for making steel is found in the Appalachians and in the areas near Lake Superior.