题目

已知向量，，且，则 A．5               B．            C．           D． 答案：D    【解析】 试题分析：若平均数为，可得，中位数为，合题意；若平均数为，可得，中位数为，合题意；若平均数为，可得，中位数为，合题意；若平均数为，可得，中位数为，不合题意；所以该运动员这场比赛得分的平均数不可能为，故选D. 考点：1、茎叶图的应用；2、中位数与平均值的性质.阅读理解。阅读短文，判断正(T)误(F)。(                                                     How to use the computer?      Today my father buys a computer for me. It has a keyboard, a monitor, a mouse and a printer. I'm very  happy because I can download some information from the Internet and print my homework. Do you  know how to use the computer? Let me tell you!  First, switch on the computer.      Then click "new document". Next you can write what you want in the new document. When you write,  you should click "save" again and again.       Sometimes I like to have a travel to some beautiful places at weekends. I can check the train timetable  on the computer. I love the computer!  What about you? (     ) 1. A computer has a keyboard, a monitor and a printer. (     ) 2. The writer knows how to use a computer. (     ) 3. The writer likes travelling. (     ) 4. The writer's mother buys her a computer. (     ) 5. The writer can use the computer to do her homework.