GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - 4T71277A2524G7UXJ

Which of the following statements about the global warming observed in the 1940s is implied by the passage? A. It was part of a climatic change that can be traced to the 1910s and 1920s. B. Its cause was not apparent to climatologists until the 1990s. C. It is doubtful that it was caused primarily by greenhouse gases produced by humans.