单选题Geothermal (地热的) energy has been used for thousands of years in some countries for cooking and heating. It is simply power derived from the Earth's internal heat. This thermal energy is contained in the rock and fluids beneath Earth's crust. It can be found from shallow ground to several miles below the surface, and even farther down to the extremely hot molten rock called magma (岩浆). A geothermal heat pump system can take advantage of the constant temperature of the upper ten feet (three meters) of the Earth's surface to heat a home in the winter while extracting heat from the building and transferring it back to the relatively cooler ground in the summer. Geothermal water from deeper in the Earth can be used directly for heating homes and offices, or for growing plants in greenhouses. Some US cities pipe geothermal hot water under roads and sidewalks to melt snow. To produce geothermal-generated electricity, well, sometimes a mile (1.6 kilometers) deep or more, are drilled into underground reservoirs to tap steam and very hot water that drive turbines linked to electricity generators. The first geothermally generated electricity was produced in Larderello, Italy, in 1904. There are three types of geothermal power plants: dry steam, flash, and binary (二元介质式). Dry steam, the oldest geothermal technology, takes steam out of fractures in the ground and uses it to directly drive a turbine. Flash plants pull deep, high-pressure hot water into cooler, low-pressure water. The steam that results from this process is used to drive the turbine. In binary plants, the hot water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to turn to vapor, which then drives a turbine. Most geothermal power plants in the future will be binary plants. There are many advantages of geothermal energy. It can be extracted without burning a fossil fuel such as coal, gas, or oil. Geothermal fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces. Unlike solar and wind energy, geothermal energy is always available, 365 days a year. It's also relatively inexpensive; savings from direct use can be as much as 80 percent over fossil fuels. But it has some environmental problems. The main concern is the release of hydrogen sulfide (硫化氢), a gas that smells like rotten eggs at low concentrations. Another concern is the disposal of some geothermal fluids, which may contain low levels of toxic materials. Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down.
单选题
What is essential to the operation of a geothermal heat pump system? ______
单选题
Two types of water with different pressures and temperatures are used to generate the steam in ______.
【正确答案】
A
【答案解析】根据题干中的Two types of water定位到第四段第三句。 细节辨析题。第四段主要介绍了三种类型的地热发电厂。其中第三句明确表明，闪蒸式发电厂使高温高压的水混入低温低压的水中，用这一过程产生的蒸汽驱动汽轮机。三种发电方式中，只有flash plants利用两种类型的水相互作用来发电，所以A为正确答案。 B干蒸汽发电厂、C汽轮机发动的电厂、D二元介质式发电厂都不是利用两种类型的水相互作用来发电的，故排除。
单选题
The geothermal energy can directly help the world ______.
【正确答案】
D
【答案解析】根据题干中的help the world判断，问题涉及地热的优势，因此定位到第五段。 综合判断题。第五段阐述了地热的种种优点，包括提取过程中不燃烧煤炭、原油等化石燃料；地热电厂产生的二氧化碳仅有相对清洁的天然气电厂的六分之一；和太阳能、风能相比，它的供给又比较稳定，可以全天候利用。D“减少碳排量，生产出清洁能源”是对这些优点的综合归纳，为正确答案。 A控制有毒物质的排放，地热能的产生与天然气相比计较清洁，但与控制有毒物质的排放无关，其中最后一段还提到地热流体还含有低毒性的物质，故排除；B减少太阳能和风能的消耗量，地热能的产生与太阳能和风能的减少与增加没有必然联系，故排除；C使电力一年365天随时可取，文中提及的是地热能一年365天随时可取，不是电力，故排除。
单选题
Concerning the sustainability of geothermal energy, people believe that ______.