21. According to Karl Pearson,only one scientific method
£ÛA£Ý prevailed in every field of study during 1890¬ðs.
£ÛB£Ý directed the collection and arrangement of facts.
£ÛC£Ý served as a unique element uniting all disciplines.
£ÛD£Ý made the identification of new knowledge plausible.

22 As stated by Hempel,general laws are
£ÛA£Ý based on detailed accounts of actual facts.
£ÛB£Ý composed of subordinate laws by deduction.
£ÛC£Ý realized in probabilistic or statistic form.
£ÛD£Ý applied to all cases or under certain conditions.

23.The author feels sure of the truth that in 19th century
£ÛA£Ý physics and history shared a common feature.
£ÛB£Ý the same method blended history with physics.
£ÛC£Ý statistical laws were compatible with physics.
£ÛD£Ý probabilistic method was inapplicable to history.

24.In the 20th century,it was true that
£ÛA£Ý universal laws ceased to belong merely to physics.
£ÛB£Ý deductive explanations became dominant in history.
£ÛC£Ý distinction between history and physics turned obscure.
£ÛD£Ý statistical explanations were adopted by physicists.

25.In the study of physical particles,
£ÛA£Ý statistical information accounts for the interest in aggregates.
£ÛB£Ý probabilistic conceptions result from their formulation.
£ÛC£Ý description of their mechanics is based on statistical data.
£ÛD£Ý physical equations are accountable for probabilistic ideas.

Text 2
    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¡ªeven 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¬ðs 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 (¿óÂö), 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 central banks to provide backing for paper currency. But the amount of gold used in arts and in industry is increasing. In addition to its use for jewelry, decorative finishes, and dentistry, its special properties have led to many applications in modern science and technology. Surface coatings of gold protect earth satellites from heat and corrosion, and certain electrical components and circuits of spacecraft are made of gold when extreme reliability is required.

    Gold was first produced in the United States from the southern Appalachian region, beginning about 1792. These deposits, though rich, were relatively small and were quickly depleted. The discovery of gold at Sutter¡¯s Mill in California sparked the gold rush of 1849¡ª50. Hundreds of mining camps sprang to life as new deposits were discovered. As a result, the production of gold increased rapidly.