Question

【题目】An increased concentration of carbon dioxide and certain other gases in the Earth’s atmosphere ______ global warming.

A. contributing to B. contribute to

C. contributes to D. to contribute to

Answer 1

【答案】C

【解析】句意：地球大气层中越来越多的二氧化碳和其他气体导致了全球变暖。分析可知An increased concentration为句子的主语，谓语动词应用单数第三人称形式。故选C。