______the library for hours without finding anything useful, I turned to my prof

游客2024-06-22  10

问题 ______the library for hours without finding anything useful, I turned to my professor for help.

选项 A、To search
B、Having searched
C、Have searched
D、Searching

答案 B

解析 考查现在分词的完成时。表示其动作在谓语动词的动作之前完成,作时间或原因状语,找资料是发生在寻求帮助之前,用having seacrched,故选B。
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