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Sharks Perform a Service for Earth’s Waters It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. Although these fish perform a valuable (52) for earth’s waters and for human beings, business and sport fishing are threatening their (53) . As a result, some sharks are at risk of disappearing from Earth. Warm weather may influence both fish and shark (54) . Many fish swim near coastal areas because of their (55) waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal (海豹) or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up, because those are the times when sharks are looking for (58) . Experts also say that bright colors and shiny jewelry (珠宝) may cause sharks to attack. A shark has an extremely ’good sense of (59) , with which it can find small amounts of substances in water, such as blood, body liquids and chemicals (60) by animals. These powerful senses help sharks find their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean. Medical researchers want to learn more about the shark’s body defense and immune (免疫的) (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the world’s oceans, as they eat injured and diseased fish. Their (64) activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.
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Water-the Issue of This Century The world is running short of fresh water. Populations are growing bigger and Thirstier(渴的), with the result that freshwater is becoming increasingly scarce (缺乏). Half the world’s wetlands have disappeared during the last century, while estimates suggest that water use will rise by 50% in the next 30 years. The World Bank report estimates that as much as half of the world’s population, concentrated in Africa, the Middle East and south Asia, will face ’severe water shortages’ by 2025. Local water conflicts and the loss of freshwater ecosystems appear large in some regions. A similar picture emerges from the globe’s salt water regions. Three-quarters of the world’s people may live within 100km of the sea in 2025, putting even more pressure on stretched coastal ecosystems. Two thirds of fisheries (渔业) are exploited at or beyond their sustainable limits, and half the world’s coral reefs (珊瑚礁) may perish in 100 years. Almost 60% of coral reefs and 34% of fish species are at risk from human activities, the Bank says. The report concludes that there is ample evidence to justify immediate and coordinated action to safeguard supplies and use water more efficiently. Fresh water consumption is rising quickly, and the availability of water in some regions is likely to become one of the most pressing issues of the 21st century. A third of the world’s population - around two billion people - live in countries that are experiencing moderate to high water shortages. That proportion could rise to half or more in the next 30 years unless institutions (制度) change to ensure better conservation and allocation of water. China is one country where the portents (征兆) are gloomy. The most water-stressed country in East Asia, China is exploiting 44% of its usable water, a figure projected to rise to 60% by 2020. Primary withdrawal of water of more than 60% is widely considered by water experts to exceed the environmental carrying capacity of a river basin system. Although China’s total use appears still to be reasonable, it has several basins that are severely stressed environmentally. Withdrawals exceed environmental limits in Afghanistan and Pakistan, and will exceed them in India by 2020. In the Middle East and North Africa, only Morocco has unexploited water resources. The rest have exceeded environmental limits and many are mining aquifers (蓄水层) - bodies of water-bearing rock - the report says. It is estimated that water use will rise by 50% in the next 30 years.
Sharks Perform a Service for Earth’s Waters It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. Although these fish perform a valuable (52) for earth’s waters and for human beings, business and sport fishing are threatening their (53) . As a result, some sharks are at risk of disappearing from Earth. Warm weather may influence both fish and shark (54) . Many fish swim near coastal areas because of their (55) waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal (海豹) or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up, because those are the times when sharks are looking for (58) . Experts also say that bright colors and shiny jewelry (珠宝) may cause sharks to attack. A shark has an extremely ’good sense of (59) , with which it can find small amounts of substances in water, such as blood, body liquids and chemicals (60) by animals. These powerful senses help sharks find their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean. Medical researchers want to learn more about the shark’s body defense and immune (免疫的) (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the world’s oceans, as they eat injured and diseased fish. Their (64) activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.
Sharks Perform a Service for Earth’s Waters It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. Although these fish perform a valuable (52) for earth’s waters and for human beings, business and sport fishing are threatening their (53) . As a result, some sharks are at risk of disappearing from Earth. Warm weather may influence both fish and shark (54) . Many fish swim near coastal areas because of their (55) waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal (海豹) or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up, because those are the times when sharks are looking for (58) . Experts also say that bright colors and shiny jewelry (珠宝) may cause sharks to attack. A shark has an extremely ’good sense of (59) , with which it can find small amounts of substances in water, such as blood, body liquids and chemicals (60) by animals. These powerful senses help sharks find their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean. Medical researchers want to learn more about the shark’s body defense and immune (免疫的) (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the world’s oceans, as they eat injured and diseased fish. Their (64) activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.
场景（二）某建筑工程，南北朝向，桩基采用锤击法施工，基础底板长×宽×厚为40m×20m×1.1m，不设后浇带和变形缝，该建筑为钢筋混凝土框架结构，普通混凝土小型空心砌块填充墙作围护结构。底板混凝土标号为C35P8，配制底板混凝土采用P．O32．5水泥，浇筑时采用1台混凝土泵从东向西一次连续浇筑完成。根据场景（二），作答下列题目： 本工程主梁、次梁、板的钢筋位置顺序是（）。
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