题目

某校100名学生的数学测试成绩的频率分布直方图如图所示，分数不低于a即为优秀，如果优秀的人数为20，则a的估计值是( ) A．130                               B．140 C．133                               D．137 答案：C [解析] 本题考查频率分布直方图．由已知可以判断a∈(130,140)，所以[(140－a)×0.015＋0.01×10]×100＝20，解得a≈133，故选C.There will be a week of training with real opera singers who would teach us about opera and how to sing, as well as making costumes and props（服装道具）. When I arrived on the first day we started learning one of our songs. It would be the opening song of the show. Later that day we could audition for a part in the story. Over the next few days we started making our props and costume with the special designers. The prop making was fun but was VERY sticky! When everything was made we started to rehearse（排演） with our masks. We were put into two singing groups, Aslant’ s army and the Queen’s army. There were four teachers with us during the week who helped us to learn about opera. They told us lots of interesting things, including how important your muscles are when you are singing and all about breathing properly. I loved the sound of different voices used in opera.  In the evening, we performed in front of a large crowd outside the forum in Norwich（挪利其广场）which made me feel a bit nervous—but I got over my nerves and I really enjoyed it. I think everybody did very well, especially the people who had to sing solos（独唱）. On the last song of performance（演出）, everyone was really strong and did his best and I think everyone had a great time. The opera boot-camp was a great week for me. It was so much fun and I really hope that Opera Brava comes back again.   1. We can learn from the passage that the training lasted for        .       A. two days             B. four days           C. seven days          D. ten days   2. What did they do on the first day of the camp?       A. They made costumes and props.          B. They learned one of their songs.      C. They rehearsed with their masks          D. They were taught how to sing   3. What did the writer think of the performance?      A. It was nervous.                                  B. It was important.      C. It was difficult.                                  D. It was a success.   4. The passage is mainly about          .       A. an opera boot-camp                            B. an opera show      C. an interesting song                             D. opera