21、Beijing had its biggest snowfall since 1951．Britain is suffering through its longest cold snap（寒潮）since 1981．And freezing weather is hitting the Deep South，including Florida’s orange groves and beaches．

Whatever happened to global warming?

Such weather doesn’t seem to fit with warnings from scientists that the Earth is warming because of greenhouse gases．But experts say the cold snap doesn't contradict global warming at all--it's just a temporary phenomenon in the long-term heating trend．"It's part of natural variability," said Gerald Meehl, a senior scientist．With global warming, he said, "we'll still have record cold temperatures．We'll just have fewer of them．"

Scientists say man-made climate change does have the potential to cause more frequent and more severe weather extremes．But experts did not connect the current cold snap to climate change．

So what is going on?

"We basically have seen just a big outbreak of Arctic air over populated areas of the Northern Hemisphere", Arndt said．

In the atmosphere, large rivers of air travel roughly west to east around the globe between the Arctic and the tropics．This air flow acts like a fence to keep Arctic air restricted．But recently, this air flow has become bent into a zigzag （之字形） pattern, wandering north and south．If yon live in a place where it brings air up from the south, you get warm weather．In fact, record highs were reported this week in Washington state and Alaska．

But in the eastern United States, like some other unlucky parts of the globe, Arctic air is coming from the north．And that's how you get a temperature of 3 degrees in Beijing, a reading of minus-42 in mainland Norway, and 18 inches of snow in parts of Britain．The zigzag pattern arises naturally from time to time, but it is not clear why it's so strong right now．

1．What is the best title of the text?

A．Freezing weather is hitting the Deep South．

B．We'll still have record cold temperatures．

C．The air flow has become a zigzag pattern．

D．Cold snap doesn't contradict global warming．

2．With global warming, we will______．

A．also meet with severe cold snap

B．have more hot temperatures forever

C．never experience cold temperatures

D．have more cold temperatures

3．According to experts, the current cold snap______．

A．suggests that the climate has changed greatly

B．is not related to the climate change

C．shows that the climate will turn cold

D．is affected by global warming

4．Beijing had its biggest snowfall since 1951 because of______．

A．a fence from the Arctic                      B．a cooling trend in climate

C．a big outbreak of Arctic air                   D．its large population

5．We can conclude that

A．not all the parts of the Northern Hemisphere are cold in face of the cold snap

B．the zigzag pattern arises naturally accidentally

C．Beijing will get cold weather next year

D．Washington state and Alaska will not face cold weather next year

19、The film "Avatar" took more than five years______ and was reportedly one of the most expensive films．

A．making          B．made         C．to make             D．to be made

18、______ is not how much you do but what you do that matters．

A．What         B．It         C．That        D．There

17、--It's so nice to enjoy the sunshine here on the green grass．

--You ______ us a right place．

A．had introduced          B．are introducing            C．have introduced          D．introduce

16、Life is like a long race ______ we compete with others to go beyond ourselves．

A．why         B．what         C．that         D．where

15、World Expo 2010 Shanghai China, a grand-scale global event, has ______ the significant theme "Better City, Better Life．"

A．abandoned           B．adopted           C．advocated           D．adapted

14、--When shall we go planting trees in the hill?

--_______ it begins to rain, so they don't need watering．

A．Not until            B．While         C．Till          D．Unless

13、The road  ______ for vehicles is under repair．Drivers are required to take some other routes．

A．meaning           B．meant          C．to mean         D．being meant