[单项选择]Throughout history, gold has been a precious material, eagerly sought and cherished. It was probably the first metal to be mined because it is beautiful and imperishable (which will always exist or cannot wear out), and because beautiful objects can be made from it-even with primitive tools. The amount of gold known to ancient peoples probably totaled not much more than the amount produced each year by the world’’s largest gold mine located in the Witwatersrand district of South Africa. Stores of gold discovered by archaeologists in Greece, Scythia, and Egypt, as well as the gold from Indian treasuries in Mexico and Peru, represented years of patient collection of small quantities from streams and veins (矿脉) , often by slave labor. 　　The essential value of gold has always been known, even before gold was used in coinage. It remains the only universally recognized standard of value in international monetary exchange. Most of the world’’s refined gold is absorbed by governments and cent
A. Surface coatings of gold protect earth satellites from radiation.
B. Most of the world’’s refined gold is used for currency backing.
C. The world’’s largest gold mine is located in South Dakota.
D. The mining of gold can be traced back to the feudal age.

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