Some people associate migration mainly with birds. Birds do travel vast distances, but mammals also migrate. An example is the caribou, reindeer that graze on the grassy slopes of northern Canada. When the weather turns cold, they travel south until spring. Their tracks are so well-worn that they are clearly visible from the air. Another migrating mammal is the Alaskan fur seal. These seals breed only in the Pribilof Islands in the Bering Sea. The young are born in June and by September are strong enough to go with their mothers on a journey of over 3,000 miles. Together they swim down the Pacific Coast of North America. The females and young travel as far as southern California. The males do not journey so far. They swim only to the Gulf of Alaska. In the spring, males and females all return to the islands, and there the cycle begins again. Whales are among the greatest migratory of all. The humpback and blue whales migrate thousands of miles each year from the polar seas to the tropics. Whales eat huge quantities of plankton. These are most abundant in cold polar waters. In winter, the whales move to warm waters to breed and give birth to their young.

1．Which of the following is not true?

      A．Whales breed in winter.                      

      B．Young whales are born in cold waters.                                

      C．Alaskan fur seals give birth to their young in one area only.      

      D．Alaskan fur seals are born in warm weather.

2．Which of the following is not described in the passage?  

   A．Whales migrate to breed and give birth to their young.  

   B．Whale-watching in Boston in summer is an attraction.  

   C．Seals breed in the north before migration.  

   D．Reindeer feed on grass.

3．How many kinds of migrating mammals are mentioned in the passage?  

   A．four                B．three            C．two              D．one

4． What is the best title for the passage?  

      A．Three types of whales                    B．Birds' migration

       C．Mammals also migrate                 D．Several kinds of migration

A cyclic(周期的) drop in the sun’s radiation can cause unusually cold winters in parts of North America and Europe, scientists say, a finding that could improve long-range forecasts and help countries prepare for snowstorms.

       Scientists have known for a long time that the sun has an 11-year cycle during which radiation measured by sunspots on the surface reaches a peak then falls. But explaining a clear link to weather has proved harder.

       “Our research confirms the observed link between solar change and regional winter climate,” lead author Sarah Ineson of the UK Met Office told the reporters in an email. The study was published in the journal Nature Geoscience on Monday.

       Her team focused on data from the recent solar minimum during 2008-2010, a period of unusual calm for the sun and extreme winters in the United States and parts of Europe that shut down air travel and disrupted(使混乱) business.

       The researchers found that a reduction in ultraviolet(UV, 紫外线) radiation from the sun can affect high-altitude wind patterns in the Northern Hemisphere(半球),causing cold winters.

       “While UV levels won’t tell us what the day-to-day weather will do, they provide the exciting prospect of improved forecasts for winter conditions for months and even years ahead. These forecasts play an important role in long-term possibility planning,” Ineson, a climate scientist, said.

       Ineson and colleagues from Imperial College London and the University of Oxford used satellite data that more accurately measures UV radiation from the sun and found a much greater change than previously thought.

       They found that in years of low activity, unusually cold air forms high in the atmosphere over the tropics（回归线）. This causes a redistribution(重新分配) of heat in the atmosphere, making easterly winds that bring freezing weather and snow storms to northern Europe and the United States and milder weather to Canada and the Mediterranean.

       When solar UV radiation is stronger, the opposite occurs.

       Ineson’s team used the data in a complex computer model that simulates (模拟) long-term weather patterns. The model successfully reproduced what scientists have observed happening in the upper atmosphere during changes in solar radiation.

       More study was needed, though. A key uncertainly in the experiment lay in the satellite data used, because it covers only a few years. “So questions remain concerning both accuracy and also applicability to other solar cycles,” she said.

50. The new finding claims cold winters in the North Hemisphere can be caused by________.

A. a sharp rise in the amount of sunspot

B. a complex computer model simulation

C. a clear link between the sun and the earth

D. a decrease in the sun’s UV radiation

51. It has long been known by scientists that ________.

A. UV radiation can affect high-altitude wind patterns.

B. there’s a clear link between the sun’s activity and weather.

C. they can predict day-to-day weather conditions from UV levels

D. the sun’s radiation reaches a peak every eleven years

52. According to the passage, the following statements are correct EXCEPT______.

A. the research team used a complex computer system to monitor the atmosphere

B. the new finding could improve long-term weather prediction

C. the years 2008-2010 were a period when the sun’s radiation fell

D. extreme winters affected air travel and business in parts of Europe

53. What will happen if the sun turns into years of high activity according to the finding?

A. Canada and the Mediterranean will have milder weather.

B. Burning hot weather will appear in northern Europe and the United States.

C. Freezing cold weather will appear in northern Europe and the United States.

D. The whole Northern Hemisphere will suffer from extreme winter day.

54. It can be inferred from the passage that ________.

A. the research doesn’t seem accurate enough due to limited satellite data used

B. long-term weather conditions can be accurately predicted depending on UV levels

C. climate scientists have just begun their research in severe weather forecast

D. research have analyzed the data collected in eleven years

A regular drop in the sun’s radiation(辐射) can cause unusually cold winters in parts of North America and Europe, scientists say, a finding that could improve long-range forecasts and help countries prepare for snowstorms.

Scientists have known for a long time that the sun has an 11-year cycle during which radiation measured by sunspots on the surface reaches a peak then falls. But explaining a clear connection to weather is harder.

“Our research confirms the observed connection between solar change and regional winter climate,” lead author Sarah Ineson of the UK Met Office told the reporters in an email. The study was published in the magazine Nature Geoscience on Monday.

The researchers found that the reducing of ultraviolet(UV，紫外线) radiation from the sun can affect high-altitude wind patterns in the Northern Hemisphere(半球), causing cold winters.

“While UV levels won’t tell us what the day-to-day weather will do, they show us the bright future of improved forecasts for winter conditions for months and even years ahead. These forecasts play an important role in long-term possibility planning,” Ineson, a climate scientist, said.

Ineson and colleagues from Imperial College London and the University of Oxford used satellite data that more accurately(精确的) measures UV radiation from the sun and found a much greater change than previously thought.

They found that in years of low activity, unusually cold air forms high in the atmosphere over the tropics. This causes a redistribution(重新分配) of heat in the atmosphere, making easterly winds that bring freezing weather and snowstorms to northern Europe and the United States and milder weather to Canada and the Mediterranean.

When solar UV radiation is stronger, the opposite occurs.

More study was needed, though. A key uncertainty in the experiment lay in the satellite data used, because it covers only a few years. “So questions remain concerning both accuracy(精确) and also applicability to other solar cycles,” she said.

1.The new finding claims cold winters in the North Hemisphere can be caused by ______.

A. a sharp rise in the amount of sunspots

B. a drop in the sun’s UV radiation

C. a complex computer model simulation

D. a clear link between the sun and the earth

2. It has long been known by scientists that ______.

A. UV radiation can affect high-altitude wind patterns

B. there’s a clear connection between the sun’s activity and weather

C. the sun’s radiation reaches a peak every eleven years

D. they can predict day-to-day weather conditions from UV levels

3. What will happen if the sun turns into years of high activity according to the finding?

A. Canada and the Mediterranean will have milder weather.

B. The whole Northern Hemisphere will suffer from extreme winter days.

C. Freezing cold weather will appear in northern Europe.

D. Burning hot weather will appear in the United States.

4. It can be inferred from the passage that ______.

A. researchers have analyzed the data collected in eleven years

B. long-term weather conditions can be accurately predicted depending on UV levels

C. the research doesn’t seem correct and true enough due to limited satellite data used

D. climate scientists have just begun their research in severe weather forecast