题目

下列命题正确的个数是（     ）①“在三角形ABC中，若,则”的逆命题是真命题；②命题或，命题则是的必要不充分条件；③“”的否定是“”；④ 若，则的逆否命题为真命题；⑤回归分析中，回归方程可以是非线性方程.A.1       B.2           C.3            D.4 答案：分析：本小题关键是考查原命题与逆命题的真假关系，说明假命题可以列举一些特殊值. 【答案】C语法填空 （共10小题；每小题1.5分，满分15分） 　　阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡括号为16—25的相应位置上。 BEIJING---World-renowned Oxford and Cambridge have come to China   16   (attract) top-rank postgraduate students in cooperation with the China Scholarship Council. Oxford made its first   17   (appear) at the China Scholarship Council's annual International Graduate Scholarship Fair,   18   opened on Saturday in Beijing. The school wants to encourage excellent Chinese students to consider   19   Oxford can offer for   20   academic and professional careers. "The students came well-prepared with specific questions and were serious about the chance," said Sherwood, director of graduate admissions and funding at Oxford, who will make   21   two stops for the fair in Wuhan and Shanghai. The University of Cambridge   22   (attend) the fair since its first session in 2009, and stresses that it would continue to invest to train students to be problem-solvers.   23   Cambridge and Oxford present at the fair in competition for   24   best and brightest, Osterfield and Sherwood agree that the two universities usually have more interest in cooperation   25   competition, except in their traditional annual boat race.