Solar energy reaching Earth is responsible for differential heating of the atmosphere and thus air circulation as wind. Some of the energy of wind is transferred to the oceans, where it causes waves and is partly responsible for oceanic currents, although Earth’s rotation also plays a role in currents. Gravitational attraction between Earth and the Sun and Moon generates tides and, along with Earth’s rotation, causes most coastal areas to experience a twice-daily rise and fall of sea level. In short, the oceans possess a tremendous reservoir of largely untapped energy.

If we could effectively harness the energy possessed by the oceans, an almost limitless, largely nonpolluting energy supply would be ensured. Unfortunately, ocean energy is diffuse, meaning that the amount of energy for a given volume of water is small and thus difficult to concentrate and use. Several ways of using ocean energy are being considered or are under development, and one is currently in use, although it accounts for only a tiny proportion of all energy production. Of the several sources of ocean energy --- temperature differences with depth; currents; waves; and tides --- only the last shows much promise for the near future.

Ocean water at depth might be as much as 25℃ colder than surface water, a difference that allows for ocean thermal energy conversion (OTEC). OTEC exploits this temperature difference to run turbines and generate electricity. The amount of energy available is enormous, but a number of practical problems must be solved before it can be used. For one thing, any potential site must be close to land and also have a sufficiently rapid change with depth to result in the required temperature difference. Furthermore, enormous quantities of warm and cold seawater would have to circulate through an electrical-generating plant, thus requiring that large surface areas be devoted to this purpose.

The concept of OTEC is more than a century old, but despite several decades of research, no commercial OTEC plants are operating or even under construction, although small experimental ones have been tested in Hawaii and Japan.

Wind-generated ocean currents, such as the Gulf Stream, which flows along the east coast of North America, also posses energy that might be tapped to generate electricity. Unlike streams that can be dammed to impound a reservoir, any electrical-generating facility exploiting oceanic currents would have to concentrate currents’ diffuse energy and contend with any unpredictable changes in direction. In addition, whereas hydroelectric generating plats on land depend on the rapid movement o water from the higher elevation to the turbines, the energy of ocean currents comes from their flow velocity, which is at most a few kilometers per hour.

The most obvious form of energy in the oceans lies in waves. Harnessing wave energy and converting it to electricity is not a new idea, and it has been used on an extremely limited scale. Unfortunately, the energy possessed by a wave is distributed along its crest and is difficult to concentrate. Furthermore, any facility would have to be designed to withstand the effects of storms and saltwater corrosion. The Japanese have developed wave-energy devices to power lighthouses and buoys, and a facility capable of providing power to about 300 homes began operating in Scotland during September 2000.

Perhaps tidal power is the most promising form of ocean energy. In fact, it has been used for centuries in some coastal areas to run mills, but its use at present for electrical generation is limited. Most coastal areas experience a twice-daily rise the fall of tides, but only a few areas are suitable for exploiting this energy source. One limitation is that the tidal range must be at least five meters, and there must also be a coastal region where water can be stored following high tide.

Suitable sites for using tidal power are limited not only by tidal range but also by location. Many areas along the U.S. Gulf Coast would certainly benefit from tidal power plants, but a tide range of generally less than one meter precludes the possibility of development. Even areas with an appropriate tidal range such as the Arctic islands of Canada offer little potential because of their great distances from population centers.

Questions:
question_stem: According to paragraph 1, both wind energy and the rotation of Earth contribute to the creation of
choices: tag: A
text: waves

tag: B
text: oceanic current

tag: C
text: a gravitational attraction between earth and the sun and the moon

tag: D
text: tides
answer_key: B
explanation: 题干问“根据第1段，风能和地球的自转都有助于产生以下哪一项？”定位原文第二句，Some of the energy of wind is transferred to the oceans, where it causes waves and is partly responsible for oceanic currents, although Earth's rotation also plays a role in current. 部分风能传递到海洋，引发海浪，同时是形成洋流的一部分原因，尽管地球的自转也在洋流形成中起作用。因此选 B 洋流

question_stem: The word “harness” in the passage is closest in meaning to
choices: tag: A
text: put into use

tag: B
text: separate out

tag: C
text: come to understand

tag: D
text: identify the location of
answer_key: A
explanation: 段落2中提到的“harness”一词在文中最接近以下哪个意思？
A. 投入使用
B. 分离
C. 了解
D. 确定位置

question_stem: According to paragraph 3, the concept of OTEC is tied to which of the following aspects of the ocean?
choices: tag: A
text: Deep waters of the ocean are often calmer than surface waters are.

tag: B
text: Enormous amounts of water are available below the surface of the ocean.

tag: C
text: Temperatures beneath the ocean’s surface water can vary greatly according to the depth of the water.

tag: D
text: Waves and tides contribute to forming land sites that are ideal for running turbines and generating electricity.
answer_key: C
explanation: 根据第3段，OTEC 的概念与以下海洋方面的哪个方面有关？
第3段提到 OTEC 利用海洋表面以下的水温差来发电，因此 OTEC 与海洋的温度差异有关
C. 海洋表面下的温度根据水深变化而变化很大。

question_stem: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
choices: tag: A
text: Although the construction and operation of OTEC plants are expensive, many commercial plants have been built in Hawaii and Japan.

tag: B
text: Although OTEC is not a new idea, experimental OTEC plants are limited, and commercial OTEC plants do not even exist.

tag: C
text: Because successful experiments using the concept of OTEC have been conducted in Hawaii and Japan for several decades, there are now commercial plants under construction.

tag: D
text: After several decades of research, small experimental OTEC plants are being expanded to operate as large commercial plants.
answer_key: B
explanation: 原句为让步转折逻辑，C 首先排除，虚假因果；同时也可排除 D，缺少主要逻辑且表述错误。在原句中发生让步和转折的部分为 although 前后的两个分句，“概念不是新的、也没有商业化的工厂” ，“尽管有些小实验工厂”。不是 A 中的“尽管很贵”排除；因此选 B

question_stem: How does the author develop the discussion in paragraph 5 on the possibility of using wind-generated currents to generate electricity?
choices: tag: A
text: By providing examples of places where ocean currents have been used successfully

tag: B
text: By describing the process by which wind-generated ocean currents produce energy

tag: C
text: By contrasting ocean currents with other sources of water-generated electricity

tag: D
text: By establishing a historical context for modern techniques of generating electricity
answer_key: C
explanation: 题干问“关于利用风生成的海洋洋流来发电的可能性，作者是如何展开讨论的？”第5段通过与其他水源发电方式进行对比，强调了使用风生成的洋流发电的难度。因此答案：C. 通过将洋流与其他水源发电方式进行对比

question_stem: By mentioning the Japanese and Scotland in paragraph 6, the author is supporting which of the following points?
choices: tag: A
text: Some countries have come to depend heavily on power generated by the waves.

tag: B
text: Unlike other countries, Scotland and Japan have had little success using energy from waves because of the effects of weather and corrosion.

tag: C
text: The use of energy from waves is better suited for industrial purposes than it is for use in homes.

tag: D
text: It is difficult to generate electricity by using ocean waves, even though it is being done to a limited extent in some places.
answer_key: D
explanation: 题干问“通过在段落6中提到日本和苏格兰，作者支持以下哪个观点？”
解析：第6段提到日本和苏格兰已经以有限的规模使用海浪能发电，但也强调了难度和挑战。因此答案：D. 通过海浪产生电力很困难，尽管在一些地方已经以有限的规模实现。

question_stem: Why does the author mention the fact that tides have been “used for centuries in some coastal areas to run mills”?
choices: tag: A
text: To compare how energy from the ocean was gotten in the past with how it is currently gotten

tag: B
text: To emphasize the difficulty of providing for the energy needs of the coastal areas

tag: C
text: To explain why some coastal areas had more energy available in the past than inland areas typically did

tag: D
text: To support the idea that the tides are probably the most easily converted source of energy from the sea
answer_key: D
explanation: 题干问“为什么作者提到潮汐已经在一些沿海地区被用于驱动磨坊的事实？”
解析：段落开头第一句提到“也许潮汐能源是最有前途的海洋能源形式”并以此作为观点进行展开。提到潮汐已经用于驱动磨坊是为了支持潮汐是一个潜在的可转化为海洋能源的观点因此答案 D. 支持潮汐可能是最容易转化为海洋能源的观点

question_stem: The word “precludes” in the passage is closest in meaning to
choices: tag: A
text: prevents

tag: B
text: presents

tag: C
text: prepares

tag: D
text: preserves
answer_key: A
explanation: 在文中，""precludes""这个词最接近以下哪个意思？
A. 阻止 B. 提出 C. 准备 D. 保存