答案及解析：
1. 文章标题分析：Soot (煤灰) and Snow：a Hot Combination
根据标题内容可以判断该文章与自然环境(环境污染)有关。
2.被选项分析：
A Soot’s Role in Changes in the Climate and the Atmosphere
B Observations of Warming in the Northern Hemisphere
C Explanation of Increased Warming Effect Caused by Soot
C Effect to Reduce Snow Albedo (反照率)
E Ways to Reduce Soot Emission
F Greenhouse Gases as the Main Factor of G1obal Warming
分析：被选项中都涉及到了文章标题所揭示的核心词，划线结构是小标题中的核心结构，也是可以用作答案线索的结构。
直接解题：
A Soot’s Role in Changes in the Climate and the Atmosphere
B Observations of Warming in the Northern Hemisphere
C Explanation of Increased Warming Effect Caused by Soot
C Effect to Reduce Snow Albedo (反照率)
E Ways to Reduce Soot Emission
F Greenhouse Gases as the Main Factor of G1obal Warming
1. Paragraph 3 __。
Soot in areas with snow and ice may play an important role in climate change.Also，if snow and ice- covered areas begin melting，the warming effect increases，as the soot becomes more concentrated on the snow surface.”This provides a positive feedback， as glaciers and ice sheets melt，they tend to get even dirtier，” said Dr.James Hansen，a researcher at NASAs Goddard Institute for Space Studies.New York.
1.C. 分析：段首句的大意和用词似乎在暗示A是答案。但是在下文中没有具体提到soot是如何改变气候的(排除A)。段落中soot出现了两次，因此重点注意包含soot的被选项： C和E.段落中没有提到有关“煤灰散发”的问题，所以排除E，选择C.
提示：在借助段首句内容的时候判断答案的时候还应该扫视一下全文。
A Soot’s Role in Changes in the Climate and the Atmosphere
B Observations of Warming in the Northern Hemisphere
C Effect to Reduce Snow Albedo (反照率)