Some scientists warn that ice near the Earth’s Poles may indeed be melting. This “polar meltdown” may be the first sign that the Earth is heating up. We could be in very serious trouble if this trend continues. It is estimated that a meltdown of as little as 10 percent of Antarctica’s ice would raise sea levels around the globe by 4 to 9 meters. Floods would cover low-lying regions and turn coastal cities like New York and New Orleans into real life underwater world.
Scientists first predicted in the 1970s that heat trapped in the Earth’s atmosphere could cause a polar meltdown. Many now believe that human activities are turning up the heat. When we burn fossil fuels like coal and oil, we add carbon dioxide(CO2) gas to the Earth’s atmosphere. Cutting down trees also makes CO2 levels raise because trees normally soak up CO2 to make food. Scientists say higher CO2 levels strengthen the “greenhouse effect” and could increase the Earth’s temperature. In fact, CO2 levels have risen by 30 percent since the Industrial Revolution of the 18th and 19th centuries.
Over the past three years, satellite measurements have shown a sea level rise of about a quarter inch worldwide. “If nothing is done to reduce fossil-fuel pollution and global warming, sea levels will rise even more.” says geologist Richard Alley.
But even Alley admits that a polar meltdown would take time. The ice in Antarctica and Arctic locks up nearly nine times the volume of water contained in all the world’s rivers and lakes. These are such big “ice cubes” and it would probably take thousands of years to melt them.
Another scientist Charles Bentley doesn’t think a meltdown will happen at all. “Even if warmer temperatures begin to melt polar-ice,” he says, “the excess moisture would most likely be redeposit as snow.” In other words, the melted ice would evaporate into the atmosphere, refreeze, and fall as rain and snow over the Poles.
What consequence of global warming is mentioned in the passage?

A．More tropical storms.	B．More tropical diseases.
C．Changes in farm productivity.	D．Coastal flooding.

Which of the following statements does the second paragraph support?

A．CO2 in the atmosphere cannot keep the heat from escaping into space.

B．The increase of CO2 gas may warm the planet and help to melt polar ice.

C．Cutting down trees helps to greatly reduce CO2 levels.

D．The end of the short-lived age of fossil fuels is already in sight.

Geologist Richard Alley most likely agrees that _______.

A．the sea-level rise can be prevented by cutting back on energy-consuming activities

B．the recent breaking off of ice blocks from Antarctica is just a natural part of a long-term cycle

C．Antarctica temperatures have significantly changed since the Industrial Revolution

D．the polar meltdown may be an accidental change of climate rather than a sign of global warming

Charles Bentley believes that a polar meltdown will not occur because _______.

A．governments around the world are beginning to reduce CO2 levels in the air

B．a melting of the polar ice cannot be achieved with the present technologies

C．the melted ice in the polar areas would change into snow and rain over the Poles

D．the sun’s heat would have no chance of being absorbed by the polar ice

In which paragraph does the author mention the immense quantities of polar ice?

A．In the second paragraph.	B．In the third paragraph.
C．In the fourth paragraph.	D．In the fifth paragraph.