第15题: [单项选择]John D. Rockefeller,______, owned 90 percent of all American oil refineries. A. as still a young man B. while still a young man C. a young man however D. in spite of a young man 参考答案:B 答案解析:[考点] 考查句子成分——插入语。 该处的插入语起限定时间的作用,意思是“还是个年轻人的时候”,因此用while引导,选B。