When US student Olivia Priedeman, 17, woke up one morning, she thought she had had a dream about making plans with a friend.
But it wasn’t a dream. Her phone showed that during the night, Priedeman had read a text message from her friend. She did it while she was fast asleep.
Reading and sending text messages while asleep—called “sleep texting”—is an unusual sleep behaviour, similar to sleepwalking. It’s also a growing concern(关心的事) among doctors: young people can’t live without their cell phones.
One in three teenagers sends more than 100 text messages a day, according to the Pew Internet & American Life Project. And at least four out of five teenagers said they sleep with their phone on or near their bed.
Elizabeth Dowdell, a professor at Villanova University in Pennsylvania, has studied sleeping texting. She said that having a phone nearby all night is a big part of the problem.
Andrew Stiehm, a sleep medicine expert with Allina Health in Minnesota, agrees. It’s possible for the part of the brain that controls motor skills (动作技能) to wake up, while the part of the brain that controls memory and judgment(判断) may be still asleep. That’s why some people can perform basic movements ---such as walking, talking, texting or even driving—while they’re sleeping. Some of Dowdell’s students said that they’re disturbed by their nighttime texting behavior. But because sleep texting is unconscious, it’s a difficult habit to break. Dowdell said she knows of some students who wear socks on their hands to keep themselves from texting.
Marjorie Hogan, a doctor at Hennepin County Medical Center in Minneapolis, Minnesota, suggests keeping all electronic devices(电子设备) outside the bedroom at certain times.  
What happened to Olivia Priedeman?

A．She sleepwalked to a friend’s house.

B．She dreamed of making plans with a friend.

C．She phoned one of her friends during the night.

D．She read a text message from her friend while asleep.

Which part the brain controls keeps awake while asleep?

A．judgment

B．language

C．memory

D．motor skills

What does the underlined word “unconscious” mean?

A．无法

B．无意识的

C．无反应的

D．无规律的

What does doctor Hogan suggest people who sleep text do?

A．Stop text during the daytime.

B．Take some medicine to control the behaviour.

C．Keep their phones out of their bedrooms while they sleep.

D．Wear socks on their hands to stop themselves from texting.

We can learn from the passage that ________.

A．It’s easy to give up a sleep texting habit.

B．One in three teenagers has a sleep texting habit.

C．Sleep texting can reduce the quality of one’s sleep.

D．Sleep texting does more harm to one’s health than sleepwalking.