the memory processes that take place while we sleep have been unclear.
Support is growing for a theory that sleep evolved so that connections between neurons(神经元) in the brain can be weakened overnight, making room for fresh memories to form the next day. 73
Now we have the most direct evidence yet that he is right. 74 The synapses in the mice taken at the end of a period of sleep were 18 per cent smaller than those taken before sleep, showing that the connections between neurons weaken while sleeping.
If Tononi’s theory is right, it would explain why, when we miss a night`s, we find it harder the next day to concentrate and learn new information — our brains may have smaller room for new experiences.
Their research also suggests how we may build lasting memories over time even though the synapses become thinner. The team discovered that some synapses seem to be protected and stayed the same size. 75 “You keep what matters,” Tononi says. A. We should also try to sleep well the night before.
B. It’s as if the brain is preserving its most important memories.
C. Similarly, when people go for a few days without sleeping, they get sick. D. The processes take place to stop our brains becoming loaded with memories. E. That’s why students do better in tests if they get a chance to sleep after learning. F. “Sleep is the price we pay for learning,” says Giulio Tononi, who developed the idea. G. Tononi’s team measured the size of these connections, or synapses, in the brains of 12 mice. 第四部分：书面表达（共两节，35 分） 第一节 （15分）
你的英国朋友Jim所在的学校要组织学生来中国旅行，有两条线路可以选择：“长江之行”或者“泰山之旅”。Jim来信希望你能给些建议。请你给他回信，内容包括：
1.你建议的线路； 2.你的理由； 3.你的祝愿。 注意：1.词数不少于50；
2.开头和结尾已给出，不计入总词数。 Dear Jim,
Yours, Li Hua
第二节 （20 分）
假设你是红星中学高三学生李华，请根据以下四幅图的先后顺序，写一篇英文周记，记录毕业前夕你们制作以“感恩母校”为主题的毕业纪念视频的全过程。 注意：词数不少于60。 提示词：视频 video
(请务必讲作文写在答题卡指定区域内)
绝密★启用前
2017年普通高等学校招生全国统一考试
英语（北京卷）参考答案
第一部分：听力理解（共三节，30分） 第一节（共5小题；每小题1.5分，共7.5分） 1.C 2. B 3. C 4. B 5.A
第二节（共10小题；每小题1.5分，共15分） 6. B 7.B 8.A
9.C 10.A
11. C 12. B 13. A 14. C 15. A 第三节（共5小题；每小题1.5分，共7.5分）
每小题1.5分。如出现拼写错误不计分；出现大小写、单复数错误扣0.5分；如每小题超过一个词不计分。
16. dictionary 17.Italy 18. Monday/Mon. 19. Acket/ACKET 20.15374 第二部分：知识运用（共两节，45分）
第一节 单项填空（共15小题；每小题1分，共15分） 21.C 22. D 23. B 24.A 25. C 26.B 27.C 28.C 29.D 30.A 31.A 32.D 33.B 34.A 35.B
第二节 完形填空（共20小题；每小题1.5分，共30分） 36. B 41. B 46. A 51. A
37. D
38. C
39. A 44. D 49. C 54. C
40. D 45. C 50. B 55. D
42. A 43. C 47. A 52. D
48. B 53. B
第三部分：阅读理解（共两节，40分） 第一节（共15小题；每小题2分，共30分） 56. B 61. D 66. C
57. C 62. B 67. A
58. B 63. A 68. A
59. D 64. C 69. D
60. B 65. D 70. C
第二节（共5小题；每小题2分，共10分）
71. C 72. E 73. F 74. G 75. B
第四部分 第一节 Dear Jim,
I’m happy receive your letter and know you’re coming to China.
Of the two trips to the Yangtze River and Mount Tai, both are highly recommended. Personally, I prefer the your along the Yangtze, the longest river and one of the mother rivers of Chinese civilization. You can learn a lot about the history of China and Chinese people. Moreover, the scenery along the river is amazing, with many well-known sightseeing spots. That’s why I think the trip along the Yangtze will be a better choice.
Hope you’ll have a good time in China. Yours Li Hua
第二节（20分） 一、内容要点：
1. 讨论分工 2. 收集素材 3. 编辑制作 4. 放映视频 二、One possible version:
Graduation finally came. My classmates and I decided to do something. After a heated discussion, we agreed on making a video to record our experiences at school.
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