Most people who own iPhones use them as their alarm clocks-making it very easy to check emails one last time before falling asleep and hard to ever feel away from work and social networks．
Several years ago， my boss fainted due to exhaustion after staying up late to catch up on work． She banged her head and ended up with five stitches （缝针）-and became what she calls a "sleep evangelist （传教士）．" Now she leaves her phone charging in another room when she goes to bed and encourages her friends to do the same．
"I sent all my friends the same Christmas gift-a lovely alarm clock-so they could stop using the excuse that they needed their very attractive iPhones by their beds to wake them up in the morning．" she said．
If your phone wakes you up in the morning， it may also be keeping you up at night． A 2008 study showed that people exposed to mobile radiation took longer to fall asleep and spent less time in deep sleep． "The study indicates that during laboratory exposure to 884 MHz wireless signals， components of sleep believed to be important for recovery from daily wear and tear are severely affected，" the study concluded．
A quarter of young people feel like they must be available by phone around the clock， according to a Swedish study that linked heavy cellphone use to sleeping problems， stress and depression． Unreturned messages carry more guilt when the technology to deal with them lies at our fingertips． Some teens even return text messages at midnight．
Most of us choose not to set limits on our nighttime availability． Nearly three quarters of people from the age of 18 to 44 sleep with their phones within reach， according to a 2012 Time poll． That number falls off slightly in middle age， but only people aged 65 and older are leaving the phone in another room as common as sleeping right next to it．



Why did the author's boss start to enjoy sleeping？ ______

A. Her friends encouraged her to sleep on time．
B. Mobile phones couldn't wake her up on time．
C. Her friends sent her a lovely clock to wake her up．
D. She got hurt due to working too late．

Why did the author's boss give her friends alarm clocks as Christmas gifts？ ______

A. Alarm clocks don't give off any radiation．
B. Alarm clocks are better at waking her friends up．
C. She advised them to replace phones with alarm clocks．
D. She used alarm clocks to remind them not to work too late．

What can we learn from the 2008 study？ ______

A. Mobile radiation makes people unable to fall asleep．
B. Mobile phones can release 884 MHz wired signals．
C. Sleep can help people fight against radiation．
D. Components of sleep can be seriously affected by wireless signals．

What is the best title for the passage？ ______

A. How Mobile Phones Affect Sleep
B. Why Alarm Clocks Are Better than Phones
C. How we can sleep better at night
D. How Mobile Phones Affect Health