题目内容：

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