托福阅读TPO47Part3阅读原文：
Coral Reefs
An important environment that is more or less totally restricted to the intertropical zone is the coral reef. Coral reefs are found where the ocean water temperature is not less than 21 °C, where there is a firm substratum, and where the seawater is not rendered too dark by excessive amounts of river-borne sediment. They will not grow in very deep water, so a platform within 30 to 40 meters of the surface is a necessary prerequisite for their development. Their physical structure is dominated by the skeletons of corals, which are carnivorous animals living off zooplankton. However, in addition to corals there are enormous quantities of algae, some calcareous, which help to build the reefs. The size of reefs is variable. Some atolls are very large—Kwajelein in the Marshall Islands of the South Pacific is 120 kilometers long and as much as 24 kilometers across-but most are very much smaller, and rise only a few meters above the water. The 2,000 kilometer complex of reefs known as the Great Barrier Reef, which forms a gigantic natural breakwater off the northeast coast of Australia, is by far the greatest coral structure on Earth.
Coral reefs have fascinated scientists for almost 200 years, and some of the most pertinent observations of them were made in the 1830s by Charles Darwin on the voyage of the Beagle. He recognized that there were three major kinds: fringing reefs, barrier reefs, and atolls; and he saw that they were related to each other in a logical and gradational sequence. A fringing reef is one that lies close to the shore of some continent or island. Its surface forms an uneven and rather rough platform around the coast, about the level of low water, and its outer edge slopes downwards into the sea. Between the fringing reef and the land there is sometimes a small channel or lagoon. When the lagoon is wide and deep and the reef lies at some distance from the shore and rises from deep water it is called a barrier reef. An atoll is a reef in the form of a ring or horseshoe with a lagoon in the center.
Darwin s theory was that the succession from one coral reef type to another could be achieved by the upward growth of coral from a sinking platform, and that there would be a progression from a fringing reef, through the barrier reef stage until, with the disappearance through subsidence (sinking) of the central island, only a reef-enclosed lagoon or atoll would survive. A long time after Darwin put forward this theory, some deep boreholes were drilled in the Pacific atolls in the 1950s. The drill holes passed through more than a thousand meters of coral before reaching the rock substratum of the ocean floor, and indicated that the coral had been growing upward for tens of millions of years as Earth's crust subsided at a rate of between 15 and 51 meters per million years. Darwin s theory was therefore proved basically correct. There are some submarine islands called guyots and seamounts, in which subsidence associated with sea-floor spreading has been too speedy for coral growth to keep up.
Like mangrove swamps, coral reefs are extremely important habitats. Their diversity of coral genera is greatest in the warm waters of the Indian Ocean and the western Pacific. Indeed, they have been called the marine version of the tropical rain forest, rivaling their terrestrial counterparts in both richness of species and biological productivity. They also have significance because they provide coastal protection, opportunities for recreation, and are potential sources of substances like medicinal drugs. At present they are coming under a variety of threats, of which two of the most important are dredging and the effects of increased siltation brought about by accelerated erosion from neighboring land areas.
托福阅读TPO47Part3阅读题目：
Passage 1
An important environment that is more or less totally restricted to the intertropical zone is the coral reef. Coral reefs are found where the ocean water temperature is not less than 21 °C, where there is a firm substratum, and where the seawater is not rendered too dark by excessive amounts of river-borne sediment. They will not grow in very deep water, so a platform within 30 to 40 meters of the surface is a necessary prerequisite for their development. Their physical structure is dominated by the skeletons of corals, which are carnivorous animals living off zooplankton. However, in addition to corals there are enormous quantities of algae, some calcareous, which help to build the reefs. The size of reefs is variable. Some atolls are very large—Kwajelein in the Marshall Islands of the South Pacific is 120 kilometers long and as much as 24 kilometers across-but most are very much smaller, and rise only a few meters above the water. The 2,000 kilometer complex of reefs known as the Great Barrier Reef, which forms a gigantic natural breakwater off the northeast coast of Australia, is by far the greatest coral structure on Earth.
1. According to paragraph 1, all of the following are needed for the growth of coral reefs?
A.a solid base to grow on
B.exposure to light
C.the presence of river-borne sediment
D.ocean temperatures of 21 °C or higher
2. the word “prerequisite” in the passage is closest in meaning to
A.precaution
B.preparation
C.requirement
D.achievement
3. According to paragraph 1, algae are important because
A.they help build coral reefs
B.they are the dominant type of sea life living on the reefs
C.they compete with coral for zooplankton
D.they are an important source of food available to corals
4.The word “complex” in the passage is closest in meaning to?
A.extension
B.system
C.region
D.variety
Passage 2
Coral reefs have fascinated scientists for almost 200 years, and some of the most pertinent observations of them were made in the 1830s by Charles Darwin on the voyage of the Beagle. He recognized that there were three major kinds: fringing reefs, barrier reefs, and atolls; and he saw that they were related to each other in a logical and gradational sequence. A fringing reef is one that lies close to the shore of some continent or island. Its surface forms an uneven and rather rough platform around the coast, about the level of low water, and its outer edge slopes downwards into the sea. Between the fringing reef and the land there is sometimes a small channel or lagoon. When the lagoon is wide and deep and the reef lies at some distance from the shore and rises from deep water it is called a barrier reef. An atoll is a reef in the form of a ring or horseshoe with a lagoon in the center.
5.According to paragraph 2, how did Charles Darwin contribute to the understanding of coral reefs?
A.He identified the main types of coral reef and explained how they were related.
B.He discovered the existence of coral reefs on a scientific voyage.
C.He proved that reefs are mostly located very close to the shore.
D.He saw the importance of reefs for the support of other marine life.
6. The word “pertinent” in the passage is closest in meaning to
A.extraordinary
B.relevant
C.intelligent
D.famous
7. According to paragraph 2, which of the following is NOT characteristics of a barrier reef?
A.It is located away from the shore of the neighboring land.
B.It is separated from neighboring land by a wide channel.
C.It is located in deep ocean water.
D.It surrounds a small, central lagoon.
Passage 3
Darwin s theory was that the succession from one coral reef type to another could be achieved by the upward growth of coral from a sinking platform, and that there would be a progression from a fringing reef, through the barrier reef stage until, with the disappearance through subsidence (sinking) of the central island, only a reef-enclosed lagoon or atoll would survive. A long time after Darwin put forward this theory, some deep boreholes were drilled in the Pacific atolls in the 1950s. The drill holes passed through more than a thousand meters of coral before reaching the rock substratum of the ocean floor, and indicated that the coral had been growing upward for tens of millions of years as Earth's crust subsided at a rate of between 15 and 51 meters per million years. Darwin s theory was therefore proved basically correct. There are some submarine islands called guyots and seamounts, in which subsidence associated with sea-floor spreading has been too speedy for coral growth to keep up.
8. 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.
A.Darwin claimed that, of the three types of coral reefs, only an atoll would be able to survive on a sinking platform.
B.Darwin recognized that coral reefs achieved success by growing upward from a sinking land platform and becoming an atoll.
C.Darwin argued that as a coral reef grew up from a sinking island, it would become a fringing reef, then a barrier reef, and finally, with the disappearance of the island, an atoll.
D.Darwin’s theory helped explain the disappearance of a number of islands by showing how coral reef growth caused them to sink below the ocean surface.
9. Which of the following can be inferred from paragraph 3 about the Pacific atolls?
A.They were once fringing reefs around the coasts of islands.
B.They were first observed by Darwin during his voyage on the Beagle.
C.They will eventually become fringing reefs.
D.They are located where the ocean floor does not sink.
10. Why does the passage provide the information that the drill holes in the Pacific atolls passed through more than a thousand meters of coral before reaching the rock substratum of the ocean floor?
A.To emphasize that according to Darwin’s view coral can grow at great depths
B.To indicate how scientists knew the rate at which Earth’s crust had subsided
C.To support the claim that coral reefs take millions of years to form
D.To present the evidence that confirmed Darwin’s account of coral reef evolution
Passage 4
Like mangrove swamps, coral reefs are extremely important habitats. Their diversity of coral genera is greatest in the warm waters of the Indian Ocean and the western Pacific. Indeed, they have been called the marine version of the tropical rain forest, rivaling their terrestrial counterparts in both richness of species and biological productivity. They also have significance because they provide coastal protection, opportunities for recreation, and are potential sources of substances like medicinal drugs. At present they are coming under a variety of threats, of which two of the most important are dredging and the effects of increased siltation brought about by accelerated erosion from neighboring land areas.
11. According to paragraph 4, why have coral reefs been compared to tropical rain forests?
A.Both are located near the Indian and western Pacific Oceans.
B.Both are home to a wide variety of species.
C.Both play an important role in protecting coastal islands.
D.Both are threatened by the erosion of nearby land.
12. The word “potential” in the passage is closest in meaning to
A.powerful
B.possible
C.valuable
D.reliable
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage.
Yet because many coral reef organisms can tolerate only a narrow range of environmental conditions, reefs are sensitive to damage from environmental changes.
Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.
Like mangrove swamps, coral reefs are extremely important habitats. Their diversity of coral genera is greatest in the warm waters of the Indian Ocean and the western Pacific. ■ Indeed, they have been called the marine version of the tropical rain forest, rivaling their terrestrial counterparts in both richness of species and biological productivity. ■They also have significance because they provide coastal protection, opportunities for recreation, and are potential sources of substances like medicinal drugs. ■At present they are coming under a variety of threats, of which two of the most important are dredging and the effects of increased siltation brought about by accelerated erosion from neighboring land areas. ■
14. 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.
Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it.
To review the passage, click VIEW TEXT.
Coral reefs constitute an important tropical environment that provides habitat for a rich variety of ocean life.
Answer Choices
A.Coral reefs are structures made by living creatures and can grow only in specific ocean conditions.
B.Although atolls can sometimes grow to large proportions, barrier reefs are by far the largest coral structures.
C.Mangrove swamps are as important as coral reefs as the habitat for numerous plant and animal species.
D.Coral reefs are classified as fringing, barrier, or atoll, all of which are linked in a chain of progressive development.
E.Although coral reefs are important to humans in several ways, they are currently threatened by dredging and mud from erosion.
F.Fringing reefs lie close to the shore of continents and islands, forming a transition zone between the land mass and the sea.
托福阅读TPO47Part3阅读答案：
Passage 1
Q 1
正确答案：C
解析：A对应原文中的a firm substratum。B对应原文中的the seawater is not rendered too dark。D对应原文中的the ocean water temperature is not less than 21°C。只有C不是珊瑚生长的必要条件。
Q 2
正确答案：C
解析：原句意为，深约30~40米的平台比较是珊瑚生长的必要前提。其中的prerequisite意为“前提，先决条件”，四个选项中，A意为“预防，防备”，B意为“准备，预备”，C意为“要求，必要条件”，D意为“成就”，只有C符合条件。
Q 3
正确答案：A
解析：A是对第1段中which help to build the reefs的同义转述，故为答案。
Q 4
正确答案：B
解析：原句意为，2000公里的珊瑚礁群被称为大堡礁，它构成了澳大利亚东北部地区的一个巨大的天然防波堤，也是目前地球上最大的珊瑚结构。 其中的complex意为“综合体，结合体”，四个选项中，A意为“伸展，扩张”，B意为“系统”，C意为“地区”，D意为“多样化，类型”，只有B符合要求。
Q 5
正确答案：A
解析：第2段提到，达尔文将珊瑚分为三大类，他还发现，这些珊瑚之间存在逻辑和等级顺序上的联系。A是对原文信息He recognized that … in a logical and gradational sequence.的综合概括，故为答案。
Q 6
正确答案：B
解析：原句意为，200多年以来，珊瑚吸引了科学家们的目光，其中1830年查尔斯·达尔文在乘坐贝格尔航行时对珊瑚礁的观察最为深入中肯。句中的pertinent意为“相关的”，四个选项中，A意为“非凡的，特别的”，B意为“相关的”，C意为“聪明的”，D意为“著名的”，只有B符合条件。
Q 7
正确答案：D
解析：第2段提到，如果环礁湖宽而且深，且礁生长在离岸边一段距离的深水中，这种珊瑚礁就叫堡礁。A、B、C分别与原文中的When the lagoon is wide and deep and the reef lies at some distance from the shore and rises from deep water it is called a barrier reef.对应。D是针对上一句中的a small channel or lagoon设置的干扰。
Q 8
正确答案：C
解析：高亮部分的句子主要阐述了三种珊瑚礁随着平台的下沉而变化的情形：fringing reef会变成barrier reef，barrier reef会变成atoll。C是对这句话的同义转述。
Q 9
正确答案：A
解析：第3段首先阐述了达尔文的理论，接着列举了the Pacific atolls的例子进行说明。结合the Pacific atolls的drill holes的深度(The drill holes passed through more than a thousand meters of coral before reaching the rock substratum of the ocean floor)以及地势下沉的幅度(Earth’s crust subsided at a rate of between 15 and 51 meters per million years)来推测，它们以前曾经是fringing reefs，故A为正确答案。
Q 10
正确答案：D
解析：第3段提到，达尔文的理论认为，三种珊瑚之间随着地势的变化也会发生相应的变化。而作者在阐述the Pacific atolls的时候，说明了其深度以及地势下沉的幅度，由此推测，现在的太平洋环形礁有可能曾是fringing reef，由此可见达尔文的理论基本正确。而且作者也在文章中阐明，Darwin’s theory was therefore proved basically correct.因此D正确。
Q 11
正确答案：B
解析：作者将珊瑚礁和热带雨林进行类比，主要是为了说明珊瑚礁在生物物种多样性和生物生产力方面的优势。B对应原文中的in both richness of species and biological productivity，故为正确答案。
Q 12
正确答案：B
解析：原句意为，它们很重要，体现在海岸防护、旅游娱乐和潜在的药用成分方面。其中的potential意为“潜在的”，四个选项中，A意为“强大的”，B意为“可能的”，C意为“有价值的”，D意为“可信的”，只有B符合条件。
Q 13
正确答案：填入第三个方框处。
解析：待插入句句首的yet提示，这句话是个过渡句，与前面的内容发生了转折。纵观四个方框前后的句子，第三个方框前的句子都是在阐述珊瑚礁物种的丰富性及其影响，而第三个方框后面的句子则开始说珊瑚礁面临的威胁，这与待插入句中的damage from environmental changes相呼应，故应填入第三个方框处。
Q 14
正确答案：ADE
解析：A对应第1段的内容。D对应第2段的内容。E对应最后一段的内容。B中的barrier reefs are by far the largest coral structures在文中未提及。C是对原文中Like mangrove swamps, coral reefs are extremely important habitats.的过度理解。F是对第2段细节内容的曲解。