It might be fun to use your smartphone, but be careful. Too much screen time may be harmful to your health.
First, it is bad for your eyes. A researcher called Sarah Hinkley says the problem comes from the blue light that the screen gives out. Looking at a smartphone for a long time can cause eye strain（劳损）, headaches and dry eyes. So it is a good idea to take a break every 15 minutes when you are working at a computer or using a smartphone.
Second, screen use can do harm to children’s brains. A new study shows that using screens too much can affect（影响） how children’s brains grow. If children use screens for more than one hour a day, they might have lower levels of white matter in their brains. White matter is a key to the development of language and reading skills. So it is wise to cut down the time of children using all kinds of screens.
Third, using screens too much will affect your sleep. According to a study, about 95% of the people between the ages of 13 and 64 use electronics before bed, especially the young people under 20. Doctors say that the light from those electronics at night may make you excited before you go to bed. Then it’s hard for you to get enough sleep. So you’d better turn off smartphones, TVs, and all other screens an hour before your bedtime.
To keep healthy, doctors and researchers strongly advise that you shouldn’t use screens for long hours.
36. The blue light from your screens can cause ________.
A. eyestrain B. headaches C. dry eyes D. all of the above
37. According to the passage, you can’t sleep well because you ________.
A. take a break every 15 minutes B. have lower levels of white matter
C. use screens too much before bed D. are the people from 13 to 64
38. Which of the following is NOT true according to the passage?
A. Using smartphones for long hours does harm to your eyes.
B. A lot of screen time affects children’s brain growth.
C. The light from electronics at night may make you excited.
D. People of all ages mustn’t use electronics.
39. You may read the passage in ________.
A. a science magazine B. a travel diary C. a guide book D. a novel
40. What is the main idea of the passage?
A. The ways to keep healthy. B. The harm of using screens too much.
C. The ways to use screens. D. The advantages of using screens.
这是一篇说明文，文章主要讲述的是屏幕使用过多对人的三点危害。
36.D【解析】细节理解题。根据第二段“Looking at a smartphone for a long time can cause eye strain, headaches and dry eyes”可知长时间看手机会引起眼劳损、头痛和干眼症。故选D。
37.C【解析】细节理解题。根据第四段“using screens too much will affect your sleep”可知睡觉之前看屏幕太多会影响睡眠。故选C。
38.D【解析】推理判断题。根据“it is bad for your eyes”可知A选项表述正确；根据“screen use can do harm to children’s brains”可知B选项表述正确；根据“the light from those electronics at night may make you excited before you go to bed”可知C选项表述正确。根据“it is wise to cut down the time of children using all kinds of screens”可知D选项“People of all ages”表述错误。故选D。
39.A【解析】推理判断题。a science magazine一本科学杂志；a travel diary一个旅行日记；a guide book一本指南；a novel一本小说。文章主要讲述使用手机时间过长对人的危害，可知文章来自科学杂志。故选A。
40.B【解析】主旨大意题。文章主要讲述是屏幕使用过多对人的危害，可概括为The harm of using screens too much。故选B。