利用接地装置的分流作用来减少通过人体的电流，从而起到避免人体遭受致命损伤的接地措施是

阅读理解。

     Social networking websites are causing alarming changes in the brains of young users, a famous scientist

has warned. Sites such as Facebook, Twitter and Bebo are said to shorten attention spans (幅度), encourage

instant satisfaction and make children more self-centered.

     Warnings from neuroscientist (神经系统科学家) Susan Greenfield will disturb the millions whose social

lives depend on surfing their favorite websites each day. But they will strike a chord (弦) with parents and

teachers who complain that many teenagers lack the ability to communicate or concentrate away from their

screens.

     More than 150 million use Facebook to keep in touch with friends, share photographs and videos and

post regular updates of their movements and thoughts. A further six million have signed up to Twitter, the

"micro-blogging" service that lets users exchange text messages about themselves. But while the sites are

popular and extremely profitable, a growing number of psychologists and neuroscientists believe they may

be doing more harm than good.

     Baroness Tarot, an Oxford University neuroscientist believes repeated exposure could rewire the brain.

Computer games and fast-paced TV shows were also a factor, she said. "My fear is that these technologies

are weakening the brain to the state of small children who are attracted by buzzing noises and bright lights,

who have a small attention span and live for the moment. often wonder whether real conversation in real

time may eventually give way to these easier and faster screen dialogues, in much the same way as killing

and butchering an animal to eat has been replaced by the convenience of packages on the supermarket shelf,"

she said.

     Psychologists have also argued that digital technology is changing the way we think. They point out that

students no longer need to plan their term papers before starting to write-thanks to word processors they

can edit as they go along.

     A study by the Broadcaster Audience Board found teenagers now spend seven and a half hours a day in

front of a screen. Educational psychologist Jane Healy believes children should be kept away from computer

games until they are seven. Most games only excite the "flight or fight" areas of the brain, rather than the

areas responsible reasoning.

     Sue Palmer, author of Toxic Childhood, said:"We are seeing children's brain development damaged because

they don't engage in the activity they have engaged in for thousands of years. I'm not against technology and

computers. But before they start social networking, they need to learn to make real relationships with people."

1. According to the passage, social networking websites might _____.

A. encourage young users constant satisfaction

B. lengthen young users' attention span

C. make young users more selfish

D. help young users communicate better with their families

2. A neuroscientist may worry that sites like Facebook may _____.

A. help children learn to make real relationships with people in society

B. encourage students not to plan their term papers before starting to write

C. disturb those whose social lives depend on surfing their favorite websites

D. make real conversation in real time give way to easier and faster screen dialogue

3. From the passage we can infer that _____.

A. Baroness Tarot agrees websites cause small children's small attention span

B. Jane Healy believes computer games can do good to children's reasoning

C. Susan Greenfield's warnings have been brought to wide public attention

D. Sue Palmer's book Toxic Childhood discusses the development of networking

4. What is the purpose of this passage?

A. To tell us the conflict between neuroscientists and psychologists on websites.

B. To present some negative opinions on social networking websites.

C. To offer advice on the problem of brain damage caused by social networking.

D. To analyse how social networking websites cause damage in the brains of teenagers.

5. From Baroness Tarot's example of "killing and butchering an animal to eat", we can learn he is worried

    that _____.

A. technologies are weakening are the brain to the state of small children

B. small children have a small attention span and live for the moment

C. real conversation in real time may be replaced by easier and faster screen dialogues

D. killing and butchering an animal to eat leads to the convenience of the supermarket

示波器增辉电路的功用是（）。

A.在扫描期间产生一个持续时间与扫描电压相等的正向方波电压，使示波管只在扫描期间产生光迹

B.产生一个正向电压，使示波器亮度增加

配送处于（）物流。

A.初始

B.末端

C.中间

D.过渡

高炉生产时，对炉缸死铁层稳定有较大影响的是（）

A、铁口角度

B、铁口深度

C、铁口孔径

D、打泥量

教学的基本组织形式是（）。它是由17世纪捷克教育家（）提出来的。中国在（）年，清政府在北京开办的（）中开始采用班级授课。