答题-托福阅读

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Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Heat reservoirs in the form of hot rock far beneath Earth's surface are a potential source of usable geothermal energy.

A.Heat reservoirs with a temperature from 80° to 180° centigrade can be used, as in France and Iceland, to heat buildings.

B.Most heat reservoirs with a temperature above 180° centigrade cannot be used for energy because they are usually too close to recent volcanic activity.

C.Experiments are under way to determine if geothermally heated waters could be used as a source of certain minerals that have been dissolved out of hot rocks deep within Earth.

D.A number of countries now use geothermal reservoirs that contain water or steam above 180° centigrade to generate electricity

E.The sinking of land above heat reservoirs and other environmental problems arise when water is pumped into a heat reservoir under high pressure.

F.A number of issues, including how to extract heat from reservoirs that do not have a natural supply of water, will significantly limit the use of geothermal energy for the foreseeable future.