choose one each

9. A logical operator indicating that the previous connected search word must appear in the search result, but the subsequent connected search word must not appear in the search result: A. Logic or B. logic and C. Logical negation D. intercept character 10. () refers to the references to the current literature, also known as the source literature. To understand the continuation, development and evaluation of the research work. A, source item B, Cited literature C, website address D, search method 11. ( ) is more powerful than the advanced retrieval function, but it requires the retrieval personnel to compile the retrieval form according to the retrieval grammar of the system. A, combined search B, expert search C, secondary search D, primary search 12.Science Citation Index Expanded, For short, SCI, means ( ). A. Science and Technology Conference Index , Science Citation Index c. Social Science Citation Index D. Index of Science and Technology Conference