3. The passage implies that which of the following steps would be the first performed by explorers who wish to maximize their chances of discovering gold?

　　(A) Surveying several sites known to have been formed more than two billion years ago

　　(B) Limiting exploration to sites known to have been formed from metamorphic fluid.

　　(C) Using an appropriate conceptual model to select a site for further exploration

　　(D) Using geophysical methods to analyze rocks over a broad area

　　(E) Limiting exploration to sites where alluvial gold has previously been found

　　4. Which of the following statements about discoveries of gold deposits is supported by information in the passage?

　　(A) The number of gold discoveries made annually has increased between the time of the original gold rushes and the present.

　　(B) New discoveries of gold deposits are likely to be the result of exploration techniques designed to locate buried mineralization.

　　(C) It is unlikely that newly discovered gold deposits will ever yield as much as did those deposits discovered during the original gold rushes.

　　(D) Modern explorers are divided on the question of the utility of simple prospecting methods as a source of new discoveries of gold deposits.

　　(E) Models based on the theory that gold originated from magmatic fluids have already led to new discoveries of gold deposits.

　　5. It can be inferred from the passage that which of the following is easiest to detect?

　　(A) A gold-quartz vein system originating in magmatic fluids

　　(B) A gold-quartz vein system originating in meamorphic fluids

　　(C) A gold deposit that is mixed with granite

　　(D) A gold deposit that has shed alluvial gold

　　(E) A gold deposit that exhibits chemical halos

　　6. The theory mentioned in line 1 relates to the conceptual models discussed in the passage in which of the following ways?

　　(A) It may furnish a valid account of ore-forming processes, and, hence, can support conceptual models that have great practical significance.

　　(B) It suggests that certain geological formations, long believed to be mineralized, are in fact mineralized, thus confirming current conceptual models.

　　(C) It suggests that there may not be enough similarity across Archean-age gold-quartz vein systems to warrant the formulation of conceptual models.

　　(D) It corrects existing theories about the chemical halos of gold deposits, and thus provides a basis for correcting current conceptual models.

　　(E) It suggests that simple prospecting methods still have a higher success rate in the discovery of gold deposits than do more modern methods.

　　7. According to the passage, methods of exploring for gold that are widely used today are based on which of the following facts?

　　(A) Most of the Earth's remaining gold deposits are still molten.

　　(B) Most of the Earth's remaining gold deposits are exposed at the surface.

　　(C) Most of the Earth's remaining gold deposits are buried and have no surface expression.

　　(D) Only one type of gold deposit warrants exploration, since the other types of gold deposits are found in regions difficult to reach.