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实数a在数轴上的位置如图所示，则 + 化简后为（） A . 7 B . −7 C . 2a−15 D . 无法确定 答案：AThe seven-member Harvard Corporation elected Faust, a noted scholar of the American South and dean of Harvard's Radcliffe Institute for Advanced Study, as the university's 28th president. The 30-member board of overseers ratified the selection.   Faust, 59, recognized the significance of her appointment. "I hope that my own appointment can be one symbol of an opening of opportunities that would have been inconceivable even a generation ago," Faust said at a news conference on campus. But she also added, "I'm not the woman president of Harvard, I'm the president of Harvard."With Faust's appointment, half of the eight Ivy League schools will have a woman as president. Her selection caused another round of debates about equality at Harvard and nationwide after Summers' remarks that genetic differences between the sexes might help explain the lack of women in top science jobs.     Faust has been dean of Radcliffe since 2001, two years after the former women's college was merged into the university as a research center with the mission to study gender issues. "This is a great day, and a historic day, for Harvard," said James R. Houghton, chairman of the presidential search committee.   Some professors have quietly complained that the 371-year-old university is appointing a fifth consecutive president who is not a scientist. No scientist has had the top job since James Bryant Conant retired in 1953; its last four have come from the fields of classics, law, literature and economics. Faust is the first Harvard president who did not receive an undergraduate or graduate degree from the university since Charles Chauncy, an alumnus of Cambridge University in England, who died in office in 1672. She attended Bryn Mawr College and the University of Pennsylvania, where she was also a professor of history.56. Who was appointed as the first female president in its 371-year history?A. A woman scientist. B. A historian without a Harvard degree.C. The historian who made the comments that genetic differences between the sexes might help explain the lack of women in top scientific areas.D. An alumnus of Harvard University.57. Which of the following is not true?A. Havard is one of Ivy League schools.B. It was unbelievable decades ago for a woman to lead such a famous university.C. Radcliffe, a former women's college, was merged into Harvard in 2001.D. Radcliffe is a research center focusing on the world's issues and those of women in particular.58. What does the underlined word in the first paragraph mean?A. agreed with   B. witnessed    C. held   D. announced59. What would be the best title for this news?A. Faust becomes Harvard's first female president.B. Being the president of Harvard is a tough job.C. Faust being named president is a story about Harvard and women.D. A historic day for Harvard and women.