文章大意：这是一篇说明文。文章主要说明了全球变暖正在将北极熊的数量推向极限，根据一项新的研究，它们可能只剩下不到100年的时间就会灭绝。文章介绍了北极熊的生活习性以及全球变暖对它们造成的影响。
1 . 阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
Global warming is pushing the number of polar bears to 1 (it) limit. According to a new study, they could have fewer than 100 years left before 2 (extinct).
Polar bears live 3 hunting seals in the Arctic Ocean, but as ice melts in that region, their habitat continues to shrink. Amounts measured at the end of the 1970s show sea ice that lasts for more than a year in the Arctic has decreased at a rate of 13% per decade.
Studies show that 4 (decline) sea ice will lead to a reduction in polar bears. They will be unable to bear the effects of climate change over the next several decades. The scientists believe polar bears will be 5 (thorough) wiped out by 2100.
“What we’ve shown 6 (be) that, first, we’ll lose the survival of bear cubs (幼熊). Although cubs will be born, the female bears won’t have enough body fat to produce milk 7 (bring) them along through the ice-free season,” said Dr. Steven Amstrup, chief scientist of Polar Bears International, to the BBC.
The study estimates that, even in a situation 8 countries achieve a moderate (适度的) reduction in greenhouse gases, several 9 (population) of polar bears will disappear. But Amstrup said, “We can make 10 difference if we have an urge to keep climate change little.”
