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　　The Arctic Ocean has given up tens of thousands more square kilometers of ice in a relentless summer of melt, with scientists watching through satellite eyes for a possible record low polar ice cap.

　　From the barren Arctic shore of a village in Canada’s far northwest, veteran observer Eddie Gruben has seen the summer ice retreating more each decade as the world has warmed. By this weekend the ice edge lay 128 kilometers at sea, but forty years ago, it was 64 kilometers out. Global average temperatures rose 1 degree Fahrenheit in the past century, but Arctic temperatures rose twice as much or even faster, almost certainly in large part because of manmade greenhouse gases, researchers say. In late July the mercury soared to almost 86 degrees Fahrenheit in this settlement of 900 Arctic Eskimos.

　　As of Thursday, the U.S. National Snow and Ice Date Center reported, the polar ice cap extended over 6.75 million square kilometers after having shrunk an average 106,000 square kilometers a day in July—equivalent to one Indiana or three Belgiums daily. The rate of melt was similar to that of July 2007, the year when the ice cap dwindled to a record minimum extent of 4.3 million square kilometers in September. In its latest analysis, NSIDC said Arctic atmospheric conditions this summer have been similar to those of the summer of 2007, including a high-pressure ridge that produced clear skies and strong melt in the Beaufort Sea, the arm of the Arctic Ocean off northern Alaska and northwestern Canada.

　　Scientists say the makeup of the frozen polar sea has shifted significantly the past few years, as thick multiyear ice has given way as the Arctic’s dominant form to thin ice that comes and goes with each winter and summer. The past few years have “signaled a fundamental change in the character of the ice and the Arctic climate,” Meier said. Ironically, the summer melts since 2007 appear to have allowed disintegrating but still thick multiyear ice to drift this year into the relatively narrow channels of the Northwest Passage. Usually, impassable channels had been relatively ice-free the past two summers.

　　Observation satellites’ remote sensors will tell researchers in September whether the polar cap diminished this summer to its smallest size on record. Then the sun will begin to slip below the horizon for several months, and temperatures plunging in the polar darkness will freeze the surface of the sea again, leaving this and other Arctic coastlines in the grip of ice. Most of the sea ice will be new, thinner and weaker annual formations, however.

　　At a global conference last March in Copenhagen, scientists declared that climate change is occurring faster than had been anticipated, citing the fast-dying Arctic cap as one example. A month later, the U.S. National Oceanic and Atmospheric Administration predicted Arctic summers could be almost ice-free within 30 years, not at the century’s end earlier predicted.

　　26.The word “retreating” (Line2, Paragraph2) most probably means________.

　　[A] withdrawing [B] moving back

　　[C] melting [D] treating again

　　27.We may infer from Paragraph 2 and 3 that____________.

　　[A] rising Arctic temperatures result completely from manmade greenhouse gases

　　[B] the summer ice edge was 192 kilometers at sea 40 years ago

　　[C] the polar ice cap was over 6.87million square kilometers in July

　　[D] the ice cap reduced to a record low minimum extent in July

　　28.We may know that summer melts made____________.

　　[A] some impassable channels covered by ice

　　[B] no contribution to the makeup change of polar ice

　　[C] thin ice become multiyear ice

　　[D] the world climate change its character

　　29.We learn from the last two paragraphs that____________.

　　[A] scientists predicted future climate changes accurately

　　[B] the polar cap diminished this summer to its smallest size on record

　　[C] the future ice may be annually formed thinness

　　[D] Arctic summers couldn’t be ice-free until next century

　　30.Which of the following is the best title for this text?

　　[A] Arctic ice lowers to its smallest size

　　[B] Arctic ice disappears under summer sun

　　[C] Why Arctic ice disappears soon

　　[D] Arctic ice closely relates to climate changes