题目内容：

    Antarctica(南极洲)’s melting ice, which has caused global sea levels to rise by at least 13.8 millimeters over the past 40 years, was thought to primarily come from the unstable West Antarctic Ice Sheet(WAIS). Now, scientists have found that the East Antarctic Ice Sheet (EAIS)—considered largely unaffected by climate change—may also be melting at an unexpectedly rapid speed.

The WAIS, whose base is below sea level, has long been considered the most likely to break down. Besides gravity, a deep current of warm water slips beneath the sheet, melting it from below until it becomes a floating shelf at risk of breaking away. In contrast, extreme cold and a base mostly above sea level are thought to keep the EAIS relatively safe from warm waters.

But as greenhouse gases warm much of the planet, driving stronger polar winds, some scientists think warm water carried by a circular current will start to invade East Antarctica’s once unassailable ice. A cooperation of more than 60 scientists last year, published in Nature, estimated that the EAIS actually added about 5 billion tons of ice each year from 1992 to 2017.

Eric Rignot of the University of California, Irvine, and colleagues combined 40 years of satellite imagery and climate modeling and found that overall Antarctica now sends six times more ice into the sea each year than it did in 1979, with the majority coming from West Antarctica. But East Antarctica was responsible for more than 30% of Antarctica’s contribution to the 13.8-millimeter sea level rise over the past 40 years. “The more we look at this system the more we realize this is fragile,” Rignot says. “Once these glaciers become unstable there is no red button to press to stop it.”

Rignot hopes the study brings greater attention to a part of Antarctica that has traditionally been understudied. Helen Fricker, a glaciologist (冰川学家) in California, agrees. “We need to monitor the entire Antarctica and we just can’t do that without international cooperation.”

1.What is the new finding of scientists?

A.The east Antarctica is losing ice at an increasing rate.

B.The west Antarctica is melting six times faster than in 1979.

C.5 billion tons of ice is added to Antarctica each year.

D.The sea level has risen by 13.8 mm over the past 40 years.

2.Which factor leads to the EAIS’s melting fast?

A.A base mostly over sea level. B.The force of gravity.

C.The invasion of a warm current. D.Extremely low temperature.

3.Which of the following best explains “unassailable” underlined in Para. 3 ?

A.Fragile. B.Unattackable.

C.Mild. D.Unstable.

4.Which way does Helen Fricker specially advocate?

A.Satellite imagery. B.Global monitoring.

C.Worldwide climate modeling. D.Worldwide combined efforts.