题目内容
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How many salmon were there every spring in British Columbia's rivers four years earlier？
A．1.3 million.
B．About 524,000.
C．About 1,824,000.
D．Above 2,000,000.
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更多“How many salmon were there every spring in British Columbia's rivers four years earlier？A．”相关的问题
Approximately 20 percent of the lakes in Scandinavia are without fish. Moreover, in Nova Scotia the【23】salmon industry may be threatened by the decrease of salmon in rivers and streams. The impact is also【24】in the waters of Ontario and Quebec, where fish populations are【25】the decline.
What potential remedies exist for the acid rain【26】？ The experts disagree. Some say new environmental laws should be【27】to control the emission of pollutants in the atmosphere. Some say that if we had known how serious acid rain was, we would have planned【28】to prevent it.【29】, all agree that if the consumption of fossil fuel were reduced, we would have less of a problem. Another【30】is that special scrubbers could be installed in smokestacks to remove a good【31】of the pollutants before they get into the atmosphere. Other ideas even include breeding more【32】fish. And research suggests that spreading lime into lakes may be effective in【33】acidity. In conclusion, it is clear that if we truly want to reduce the impact of acid rain, a【34】of remedies and international cooperation must be explored. It is a sad fact that acid rain probably could have been avoided if we【35】what we know now.
(21)
A．Likewise
B．Besides
C．Thus
D．Otherwise
What potential remedies exist for the acid rain 【C6】______？ The experts disagree. Some say new environmental laws should be 【C7】______ to control the emission of pollutants in the atmosphere. Some say that if we had known how serious acid rain was, we would have planned 【C8】______ to prevent it. 【C9】______, all agree that if the consumption of fossil fuel were reduced, we would have less of a problem. Another 【C10】______ is that special scrubbers could be installed in smokestacks to remove a good 【C11】______ of the pollutants before they get into the atmosphere. Other ideas even include breeding more 【C12】______ fish. And research suggests that spreading lime into lakes may be effective in 【C13】______ acidity. In conclusion, it is clear that if we truly want to reduce the impact of acid rain, a 【C14】______ of remedies and international cooperation must be explored. It is a sad fact that acid rain probably could have been avoided if we 【C15】______ what we know now.
【C1】______
A．Likewise
B．Besides
C．Thus
D．Otherwise
Section B
The annals of natural history contain many astonishing examples of the ability of animals to find their way home after making distant journeys. Salmon, for example, are born in freshwater streams and soon afterward journey down to sea. Several years later, after they have attained maturity, they swim back upstream to spawn and, in many cases, to die. The particular stream that serves as the journey's end is almost invariably the same one in which they were born. It is chosen out of dozens or hundreds of equally suitable streams. The expression "almost invariably" is used advisedly in this case. In one investigation by Canadian biologists, 469,326 young sockeye salmon were marked in a tributary of the Fraser River. Several years later almost 11,000 were recovered after they had completed a return journey to the very same stream, but not a single one was ever recovered from other streams nearby. What underwater guideposts can these fish possibly follow？ It has been discovered by A. D. Hasler and his associates at the University of Wisconsin that the salmon, like many other fish, have an acute sense of smell and are able tore member slight differences in the chemical composition of water. The most reasonable theory to explain salmon homing is that each individual remembers the distinctive "fragrance" of its native stream. As it moves upstream it makes the correct choice each time a new tributary is encountered, until finally it arrives home.
Long-distance migration is especially common in birds, because many species must make annual journeys between their nesting grounds and prime feeding areas far away. Each year over 100,000 sooty terns, an attractive tropical sea bird, travel from the waters off the west coast of Africa all the way across the Atlantic to Bush Key, a tiny island near the tip of Florida. Here they build their nests and breed. Once the young can fly, all journey back over the Atlantic. Why do the sooty terns migrate at all？ Like many other seabirds, they find protection from cats, foxes, and other predators on isolated islands. It is evidently safer for them to make an entire transoceanic voyage to reach one such haven than it would be to try to nest on the nearby African shores. A somewhat different reason lies behind the north-south migration of birds in the temperate zones. Each spring a legion of migratory forms, from robins, thrushes, and warblers to geese and ducks, makes its way north into the greening countryside, where large quantities of food are becoming freshly available. Working rapidly, they are able to rear one or more broods of young. As winter approaches and the food supply declines, all head south again. Some species proceed all the way to Central and South America. The record annual journey in the Western Hemisphere is made by the golden plover, one group of which travels from northern Canada to southern South America. A second group of the same species migrates from Alaska to Hawaii and the Marquesas Islands. Human beings could never make such journeys unaided by maps and navigational instruments. How do the birds do it？ A large part of the answer lies in their ability to use celestial clues. At migration time, caged starlings become unusually restless. If permitted to see the sun, they begin to fly toward the side of the cage that lies in the direction of their normal migration route. However, when the sky is overcast and the sun is obscured from view, their movements persist, but they are non directional. Other migratory birds fly at night and can evidently use the position of the stars to guide them. This surprising fact has been established by several biologists, including S. T. Emlen of Cornell University, who allowed a type of bird called indigo buntings to attempt flights under the artificial night sky of a planetarium. The birds oriented "correctly" with reference to the planetarium sky even when the positions of its constellations did not correspond with the position of the true constellations outside. Thus other outside influences were eliminated, and it could be concluded that the birds were able to orient to what they believed to be the position of the stars.
SUMMARY:
Animals are able to get back home after they make long journeys. Salmon, for example, are known to swim back several years later to【51】where they were born. What guide these fish upstream.9 According to scientists at the University of Wisconsin, salmon【52】and follow the fragrance of their native stream as they have a sharp【53】
Birds also make long distance migration each year. Sooty terns, a type of tropical sea bird, travel across the Atlantic from Africa to an island near Florida, where they breed and can【54】from predators. Birds also migrate in order to find food and rear their young. It is discovered that birds are aided by【55】to make distant journeys that even human beings cannot make without the assistance of navigational instruments.
(66)
How many suspects were arrested？
A．17.
B．7.
C．1.
D．None.
How many states of the Council’s were there approving the resolution？
A．15.
B．13.
C．50.
D．30.
How many shoes ___ this year？
A、have been produced
B、were produced
C、produced
How many crew members were aboard the ship at the time of the kidnapping？
A．13.
B．11.
C．15.
D．16.
How many persons were killed in the hostage crisis？
A．5.
B．6.
C．7.
D．8.
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