题目

Polar bears have patrolled the planet's icy regions for millions of years longer than previously thought - riding out several episodes of global warming in that time. While this suggests their future might not be so bleak, it does not ensure that they will survive the melting occurring in the polar regions today.An international team of researchers has just completed the most comprehensive analysis yet of the polar bear genome (基因组). The team examined DNA from 23 living polar bears and a 110,000-year-old polar bear jawbone. Aided by comparisons with the genomes of brown and black bears, they found that polar bears first emerged as a separate species between four and five million years ago. Previous studies had suggested the species didn't diverge (分化) from brown bears until much later - perhaps just 600,000 years ago.The analysis also showed that polar and brown bears have sometimes interbred (杂交) since their initial divergence and that populations of polar bears have been changing over the past million years in accordance with the climate. Polar bear numbers dropped during warm periods but soared again with prolonged ice ages - most noticeably during a cooling period between 800,000 and 600,000 years ago. The population looks set to fall again as melting pack ice forces polar bears back to the land-based habitats (栖息地) of brown bears, where interbreeding can occur.What does the author say about the future of polar bears?()A We cannot be sure whether they will survive.B They will not survive due to the melting occurring in the polar regions today.C They will certainly survive after patrolling the planet's icy regions for millions of years.D We can help them to ride out the global warming this time again.

Polar bears have patrolled the planet's icy regions for millions of years longer than previously thought - riding out several episodes of global warming in that time. While this suggests their future might not be so bleak, it does not ensure that they will survive the melting occurring in the polar regions today. An international team of researchers has just completed the most comprehensive analysis yet of the polar bear genome (基因组). The team examined DNA from 23 living polar bears and a 110,000-year-old polar bear jawbone. Aided by comparisons with the genomes of brown and black bears, they found that polar bears first emerged as a separate species between four and five million years ago. Previous studies had suggested the species didn't diverge (分化) from brown bears until much later - perhaps just 600,000 years ago. The analysis also showed that polar and brown bears have sometimes interbred (杂交) since their initial divergence and that populations of polar bears have been changing over the past million years in accordance with the climate. Polar bear numbers dropped during warm periods but soared again with prolonged ice ages - most noticeably during a cooling period between 800,000 and 600,000 years ago. The population looks set to fall again as melting pack ice forces polar bears back to the land-based habitats (栖息地) of brown bears, where interbreeding can occur. What does the author say about the future of polar bears?() A We cannot be sure whether they will survive. B They will not survive due to the melting occurring in the polar regions today. C They will certainly survive after patrolling the planet's icy regions for millions of years. D We can help them to ride out the global warming this time again.

题目解答

答案

我们来一步步分析这道题。

一、题目要求：

问题是：“作者对北极熊的未来说了什么？”

选项是：

A. 我们不能确定它们是否会生存下来。
B. 它们会因为今天极地地区正在发生的融化而无法生存。
C. 它们在冰原上巡逻了几百万年，因此肯定能生存下来。
D. 我们可以帮助它们再次度过全球变暖。

二、理解文章内容：

文章讲的是一个关于北极熊基因组的研究结果，主要内容包括：

  1. 北极熊的历史比我们之前认为的要长得多，它们在几百万年前就分化出来了，而不是之前认为的60万年前。
  2. 它们经历过多次全球变暖，但依然存活了下来。
  3. 然而，作者指出，虽然北极熊在历史上成功应对过气候变化，但这次的情况可能不同。
  4. 现在的极地冰盖正在快速融化，迫使北极熊进入棕熊的栖息地，导致它们杂交，这可能威胁它们的种群纯度和生存。
  5. 文章最后说：“这并不保证它们能挺过今天极地地区正在发生的融化。”

三、选项分析：

A. 我们不能确定它们是否会生存下来。
✅ 这个选项是正确的。文章虽然提到北极熊在历史上存活下来，但明确指出“这并不保证它们能挺过今天极地地区正在发生的融化”，也就是说，作者对北极熊的未来持不确定态度。

B. 它们会因为今天极地地区正在发生的融化而无法生存。
❌ 这个选项太绝对了。文章并没有说它们“一定”会灭绝，而是说“不能保证”它们能存活。

C. 它们在冰原上巡逻了几百万年，因此肯定能生存下来。
❌ 这个选项是错误的。文章虽然提到它们历史久远，但强调“这并不保证它们能挺过今天的情况”。

D. 我们可以帮助它们再次度过全球变暖。
❌ 文章中没有提到人类可以帮助北极熊，也没有任何关于人类干预的内容。

四、正确答案：

$\boxed{A}$

解析

考查要点：本题主要考查学生对文章主旨的理解，特别是作者对北极熊未来命运的判断。需要结合文章中的关键句，分析作者的隐含态度。

解题核心思路：

  1. 定位关键句：文章首段明确指出“这并不保证它们将生存”，这是解题的核心依据。
  2. 排除干扰项：需注意选项B、C、D的绝对化表述（如“not survive”“certainly survive”“help them”）与文章中“不确定”的态度不符。
  3. 逻辑对应：北极熊虽有历史适应能力，但当前环境变化可能不同，因此未来存在不确定性。

关键信息梳理：

  • 历史背景：北极熊比之前认为的更早分化（4-5百万年前），曾多次适应全球变暖。
  • 当前挑战：极地冰盖融化导致北极熊栖息地改变，可能与棕熊杂交，威胁种群纯度。
  • 作者态度：明确指出“这并不保证它们能挺过今天极地地区正在发生的融化”。

选项分析：

  • A选项：与文章“不能保证”直接对应，正确。
  • B选项：错误，文章未断言“无法生存”，仅说明“不确定”。
  • C选项：错误，历史适应能力≠必然存活，作者已明确否定。
  • D选项：错误，文章未提及人类干预，属过度推断。