答案及解析：
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
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）
E Ways to Reduce Soot Emission
F Greenhouse Gases as the Main Factor of G1obal Warming
2． Paragraph4 __
（Hansen found soot’s effect on snow albedo （solar energy reflected back to space），which may be contributing to trends toward early springs in the Northern Hemisphere，such as thinning Arctic sea ice，melting glaciers and permafrost）．Soot also is believed to play a role in changes in the atmosphere above the oceans and land．
2．A．分析：因为段落中soot出现了两次，因此重点注意包含soot的被选项： A和E，同样段落中没有提到有关“煤灰散发”的问题，所以判断A是答案（段落最后一句（观点句）的含义与A一致）
提示：“避重就轻法”—段首句复杂则看段未句。
B Observations of Warming in the Northern Hemisphere
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
3． Paragraph 6 __．
Hansen cautioned，although the role of soot in altering global climate is substantial，it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century．Such gases are expected to be the largest climate forcing for the rest of this century．
3． F。 分析：因为段落中gas出现了两次，因此重点注意包含gas的被选项：F。而F中的内容正好与段首句中的核心结构（it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century（它没有改变‘温室效应是在过去的世纪中造成气候变暖的主要原因’这个事实））一致。
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