Many people use their mobile phones as the alarm clock and are more used to checking e-mails before sleeping. However, these habits are becoming sleeping problems.
Several years ago, my boss used to stay up working on her mobile phone and got badly ill because of that. Now she always leaves her phone in another room at night. And she encourages friends to do so. “I sent each of my friends the same christmas gift – an alarm clock so that they could stop using their phones as the alarm clock,” she said.
If your mobile phone wakes you up in the morning, it may also be keeping you up at night. A study in 2008 showed that people in mobile phone radiation（辐射）mostly had sleeping problems. And according to a Swedish study, a quarter of young people in this country feel like there must be phones around them. Most of them feel sorry for not returning messages. So they even have to reply to their friends before sleeping.
So what kind of people prefer to use mobile phones in their bedrooms? A recent study has shown that three-quarter people aged between 18 and 34 prefer to sleep with their phones near them. That number falls off a little in middle age, but only people aged 65 and older are used to leaving the phone in another room while sleeping.
The underlined word “that” refers to “_____”.

A．using the mobile phone as the alarm clock

B．checking e-mails

C．staying up working on the mobile phone

D．leaving the mobile phone in the bedroom

According to the Swedish study, ____ of young people in Sweden always put phones around them while sleeping.

A．25%

B．50%

C．75%

D．100%

According to the recent study, people _____ prefer to sleep with their phones near them.

A．aged 12 and 18	B．aged between 18 and 34
C．in middle age	D．aged over 65