The damming of river systems in the northwestern United States has had damaging effects on salmon. In the spring young salmon, called smolts, drift into rivers from smaller streams. They swim with the 题目和参考答案——青夏教育精英家教网—

题目内容

The damming of river systems in the northwestern United States has had damaging effects on salmon(鲑鱼). In the spring young salmon, called smolts, drift into rivers from smaller streams. They swim with the current downstream heading for the Pacific Ocean. Before the large-scale constructions of dams(水坝), the young salmon used the strong flow from melting snows to get to the sea in between six and twenty days. It is necessary to do this because during these days the smolts’ bodies undergo the physiological changes for adaptation to salt water.
Unfortunately, the current has become very slow due to the construction of numerous dams. Companies operating the dams also intentionally slow the current. They store the water from the melting snow until the winter, when more electric power is needed. The net result is that many of the young fish do not survive the now sixty-day trip to the sea. Consequently, there are fewer adult salmon to migrate(回游) back up the rivers for breeding. When the time comes for the salmon to return, they again face the problem of dams. As fewer adult salmon are able to get back to their cool upstream water, they fail to produce a sufficiently new generation of salmon. This cycle could eventually lead to the extinction of the fish.
Attempts are being made to transport the young salmon down river by boats. However, many scientists think that this artificial method of getting the fish to the sea kills more than it saves. Another suggestion, recently proposed by environmentalists, is to increase the rate of water flow. This would be a partial（部分的） solution to the declining salmon numbers. One method of doing this would call for releasing water from upstream dam. This would speed up the downstream movement of the smolts.
Another method would be to reduce the water level in the dams for a period in the spring when the smolts are migrating downstream. This would also increase the flow rate temporarily without requiring large amounts of water and, thus, enable the young salmon to move downstream faster. Unfortunately, both of these proposals have met with criticism from the power companies, which strongly suggests the uncertain fate of the salmon in the region.
76. What’s the main topic of the passage?
A. The failure of adult salmon to reproduce.
B. The importance of smolts returning upstream.
C. The need for smolts to reach salt water quickly.
D. The harm caused to salmon by river damming.
77. The passage discusses all of the following methods of dealing with salmon issue EXCEPT _____.
A. carrying the fish in boats
B. allowing water to be released from upstream dams
C. dropping water levels in dams
D. breeding salmon
78. In paragraph 3, what does the author mean by the statement that many scientists think that this artificial method of getting the fish to the sea kills more than it saves?
A. Saving fish is artificial.
B. More fish die when transported than would die otherwise
C. Artificial methods of transportation give salmon the chance to get adapted to salt water.
D. The sea kills more fish than are saved by transportation.
79. Which of the following statements would the author most probably agree with?
A. The salmon problem is likely to continue.
B. A solution to the salmon problem will be found in the near future.
C. Salmon will be extinct very quickly.
D. The government should step in and provide a way out.

76-79 D D B A

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Climate change，pollution，overuse of water and development are killing some of the world’s most famous rivers including China’s Yangtze．India’s Ganges and Africa’s Nile．WWF said on Tuesday．At the global launch of its report “World’s Top 10 Rivers at Risk”，the group said many rivers could dry out, affecting hundreds of millions of people and killing unique aquatic（水生的）life．

“If these rivers die，millions will lose their livelihoods，biodiversity（生物多样性）will be destroyed on a massive scale，there will be less fresh water and agriculture，resulting in less food security，”said．Rayi Singh，secretary—general of WWF—India．The report launched ahead of “World Water Day” today，also cited the Rio Grande in the United States，the Mekong and Indus in Asia，Europe’s Danube, La Plata in South America and Australia’s Murray—Darling as in need of greater protection．

Rivers are the world’s main source of fresh water and WWF says about half of the available supply is already being used up．Dams have destroyed habitats and cut rivers off from their flood plains．while climate change could affect the seasonal water flows that feed them，the report said．Fish populations，the top source of protein and overall life support for hundreds of thousands of communities worldwide，are also being threatened, it found．．The Yangtze basin is one of the most polluted rivers in the world because of decades of heavy industrialization，damming and huge influxes（流入）of sediment（积淀）from land conversion．

Climate change，including higher temperatures，also means serious consequences for fishery productivity，water supply and political security in Africa’s arid Nile basin．Tributaries（支流）flowing into the Ganges are drying up because of irrigation，WWF said．

1.hat is the text mainly about?

A．Saving fresh water in our life． B．How to protect our rivers．

C．An important discovery． D．World’s top 10 rivers are at risk．

2.We can infer from the text that _____．

A．rivers’ dying out could affect food security

B．there are four Asian rivers mentioned in the passage

C．the Yangtze is polluted thanks to the lack of enough tributaries

D．higher temperatures couldn’t affect fishery productivity

3.The top 10 rivers are fast dying as a result of the following EXCEPT _____．

A．climate change B．wasting water C．pollution D．dams

4.WWF is probably a name of _____．

A．an organization B．a newspaper C．a magazine D．a report

Unfortunately, the current has become very slow due to the construction of numerous dams. Companies operating the dams also intentionally slow the current. They store the water from the melting snow until the winter, when more electric power is needed. The net result is that many of the young fish do not survive the now sixty-day trip to the sea. Consequently, there are fewer adult salmon to migrate(回游) back up the rivers for breeding. When the time comes for the salmon to return, they again face the problem of dams. As fewer adult salmon are able to get back to their cool upstream water, they fail to produce a sufficiently new generation of salmon. This cycle could eventually lead to the extinction of the fish.

Attempts are being made to transport the young salmon down river by boats. However, many scientists think that this artificial method of getting the fish to the sea kills more than it saves. Another suggestion, recently proposed by environmentalists, is to increase the rate of water flow. This would be a partial（部分的） solution to the declining salmon numbers. One method of doing this would call for releasing water from upstream dam. This would speed up the downstream movement of the smolts.

Another method would be to reduce the water level in the dams for a period in the spring when the smolts are migrating downstream. This would also increase the flow rate temporarily without requiring large amounts of water and, thus, enable the young salmon to move downstream faster. Unfortunately, both of these proposals have met with criticism from the power companies, which strongly suggests the uncertain fate of the salmon in the region.

76. What’s the main topic of the passage?

A. The failure of adult salmon to reproduce.

B. The importance of smolts returning upstream.

C. The need for smolts to reach salt water quickly.

D. The harm caused to salmon by river damming.

77. The passage discusses all of the following methods of dealing with salmon issue EXCEPT _____.

A. carrying the fish in boats

B. allowing water to be released from upstream dams

C. dropping water levels in dams

D. breeding salmon

78. In paragraph 3, what does the author mean by the statement that many scientists think that this artificial method of getting the fish to the sea kills more than it saves?

A. Saving fish is artificial.

B. More fish die when transported than would die otherwise

C. Artificial methods of transportation give salmon the chance to get adapted to salt water.

D. The sea kills more fish than are saved by transportation.

79. Which of the following statements would the author most probably agree with?

A. The salmon problem is likely to continue.

B. A solution to the salmon problem will be found in the near future.

C. Salmon will be extinct very quickly.

D. The government should step in and provide a way out.

Climate change, pollution, overuse of water and development are killing some of the world’s most famous rivers including China’s Yangtze, India’s Ganges and Africa’s Nile, WWF said on Tuesday．At the global launch of its report “World’s Top 10 Rivers at Risk”, the group said many rivers could dry out, affecting hundreds of millions of people and killing unique aquatic life．

“If these rivers die, millions will lose their livelihoods, biodiversity will be destroyed on a massive scale, there will be less fresh water and agriculture, resulting in less food security,” said Rayi Singh, secretary-general of WWF-India．The report launched ahead of “World Water Day” today, also cited the Rio Grande in the United States, the Mekong and Indus in Asia, Europe’s Danube, La Plata in South America and Australia’s Murray-Darling as in need of greater protection．

Rivers are the world’s main source of fresh water and WWF says about half of the available supply is already being used up．Dams have destroyed habitats and cut rivers off from their flood plains while climate change could affect the seasonal water flows that feed them, the report said．Fish populations, the top source of protein and overall life support for hundreds of thousands of communities worldwide, are also being threatened, it found… The Yangtze basin is one of the most polluted rivers in the world because of decades of heavy industrialization, damming and huge influxes of sediment from land conversion．

Climate change, including higher temperatures, also means serious consequences for fishery productivity, water supply and political security in Africa’s arid Nile basin．Tributaries flowing into the Ganges are drying up because of irrigation, WWF said．

1.What does the text mainly talk about?