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 how children’s brains grow. If children use screens for more than one hour a day, they might have lower levers of white matter in their brains. White matter is the 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 age 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.

【小题1】What does the underlined word “affect” in Paragraph 3 mean? ________.

A．促进

B．宣布

C．影响

D．计算

【小题2】According to the passage, you can’t sleep well because ________.

A．the screens give out the blue light	B．you use screens too much before bed
C．you have lower levers of white matter	D．doctors ask you to use the electronics

【小题3】Which of the following is TRUE according to the passage? ________

A．The blue light can cause eye strain, headaches and dry eyes.

B．White matter is the key to the development of writing skills.

C．95% of the people under the age of 20 use electronics before bed.

D．TV programs can make the people more excited than smartphones.

【小题4】The writer’s main purpose of writing the passage is ________.

A．to show you how to use smartphones	B．to let you take a break every 15 minutes
C．to tell you advantages of using screens	D．to ask you not to use screens too much