Most polar bears could disappear by the end of the century, scientists say. Global warming is to blame. According to a study published in Nature Climate Change, most polar bear populations will be in serious decline by 2080. The cause is melting sea ice. Polar bears hunt seals on the ice. Without ice, the bears must roam on the shore, where they are spending more and more time away from their main food source. That means the animals could starve. 

“There’s not enough food on land to sustain a polar bear population,” Péter K. Molnár, the study’s lead author, said. Lack of food leads to another problem: Mother bears may not be fat enough to produce milk for their cubs. Some bear populations could stop having babies, leading to a rapid decline in numbers. 

Arctic sea ice usually melts in the spring and summer, and then grows in the winter. But now, the ice is taking longer to grow back. Weather statistics say the Arctic is warming twice as fast as the rest of the planet. Ice in the region has declined 13% every 10 years since the 1970s. The Arctic is home to roughly 25,000 polar bears. Scientists have long known that the animals are in danger. This study, which looked at 13 of the world’s 19 polar bear populations, is the first to identify when they could become extinct.

But the study also notes that it is still possible to slow Arctic melting. The world can reduce the burning of fossil fuels and lower the greenhouse gas emissions that contribute to climate change. It would have to be a drastic reduction. Bringing emissions to only a moderate level will still mean the loss of some polar bears. Saving the bears is up to us, Molnár says. “I believe that there is hope,” he says. “But humans need to act quickly to turn that hope into a reality.”

1.What is the consequence of melting sea ice according to the text?

A Seals die in large quantities.

B Seals can have more babies.

C Polar bears are short of food.

D Polar bears find food on the shore.

解析：选C。C 细节理解题。根据第一段倒数第二句“Without ice, the bears must roam on the shore, where they are spending more and more time away from their main food source.”没有冰，北极熊必须在海岸上游荡，在那里它们花越来越多的时间远离它们的主要食物来源。即北极海冰融化会导致北极熊缺少食物。故选C。

2.Which of the following statements is TRUE about the study?

A It started in the 1970s.

B It studied about 25,000 polar bears.

C It studied 19 polar bear populations.

D It identified when polar bears could disappear.

解析：选D。D 细节理解题。根据第三段最后一句“This study...is the first to identify when they could disappear”可知，这项研究首次确认了北极熊可能灭绝的时间。故选D。

3.What does Molnár think of saving the bears?

A It’s too late to do anything.

B It requires immediate action.

C It depends only on polar bears.

D It necessarily brings loss to humans.

解析：选B。B 推理判断题。根据最后一段中的“‘I believe that there is hope,’ he says. ‘But humans need to act quickly to turn that hope into a reality.’”可知，人类需要迅速采取行动拯救北极熊。故选B。

4.What’s the best title of the text?

A Climate Change in the Arctic.

B How to Protect Polar Bears.

C Polar Bears Need More Food.

D Polar Bears Are in Great Danger.

解析：选D。D 主旨大意题。文章第一句“Most polar bears could disappear by the end of the century, scientists say.”是本文主题句，科学家称到本世纪末，大多数北极熊可能会消失。因此D项“北极熊处于极大的危险之中”最符合本文大意。故选D。