阅读下面短文，从每小题所给的A、B、C、D四个选项中选出最佳选项。
C
While many people say that carrying a mobile phone makes us safer, some new research suggests the opposite is true．
Mostly we like the fact that carrying our mobile phones means we can keep in touch with our friends so easily，and text our parents to let them know where we are．But does having a phone lead people to take more risks? A recent study of teenagers' habits suggests that carrying a mobile phone can give a wrong sense of being safe．
The report shows that teenagers are more likely to travel into dangerous areas at night if they carry a phone．
"It's like you think：It'll be all right—I can always phone for help if I get into trouble．" says Ana，who was mugged(抢劫) late one evening in Gateshead last year．"But when a mugger truly flashes a knife at you and grabs your bag, the last thing you do is ring someone．"
At the same time，hospitals across the country report that the number of accidents in relationship to teenagers talking on the phone while walking along has been increasing．Dr．Zephaniah says，"It's the same as people using mobile phones while driving a car or riding a bike．You're busy thinking about what you are saying，and fail to really give your attention to where you are going or what is happening around you．"
Most accidents are small cuts，which，for example，are caused by walking into a street tree; some can be broken arms through tripping over pavements(人行道)．But there have been accidents in which teenagers have stepped off the kerbstone(路缘石)in front of a speeding car．
"He was just walking along，sending text messages on his mobile．Suddenly he stepped off the pavement in front of me without looking. I couldn't stop．"says Moira，who knocked down 14-year-old Sanjeev Singh last year．"Even though the police told me that I hadn't done anything wrong．I still can't get over it．That family will never return to their normal life after their loss but neither will I．"
So，use your phone to keep you safe．But don't let your phone lead you into danger．
满足
，那么下列选项中不一定成立的是（ ）