Teens who become addicted to their cell phones may be placing their health at risk by harming their ability to sleep well，a new Swedish study suggests. 'The message is that teenagers who use their cell phones excessively are much more stressed, much more restless, much more tired, and have a great tendency to develop sleep deprivation(剥夺) as a result of their calling habits, ' said the study author Dr. Gaby Bader. He focused on the experiences of 21 healthy Swedish boys and girls between the ages of 14 and 20. The teens kept what the authors described as 'regular working/studying hours' and were not previously diagnosed with any particular sleep irregularity． He observed that the above-15 call group kept more irregular sleeping hours than the lower-use group，had more difficulty falling asleep，more difficulty waking up，and experienced more sleep disruptions（扰乱）． Bader said that among young people，a relatively recent technological invention like the cell phone has quickly become existed nearly everywhere，giving rise to considerable pressure to keep in touch. And this pressure can develop into an addiction，with serious negative results for teenager health. 'We see more and more people--especially the young generation-- who grew up with these kinds of items and gadgets in their hands,' Bader said. 'And they become dependent on the technology. So，we have to teach young people to be structured. To know when to have the cell phone on，and when to switch it off. To avoid becoming the slave of technology，instead of the master. ' Dr. Mary Carskadon expressed little surprise with the finding. ' Interpersonal（人际的）contact is one of the things that's best at keeping us awake，' she observed. 'And so，a young person receiving cell phone texts or phone calls is going to have more deep disturbances. And they are going to be tired and restless，and probably，as a result，going to use more stimulants（兴奋剂）．And judgment is not always the best in our teenage years. So, that's where I think parental attention to this issue may be useful. ' 72. Teens who become addicted to their cell phones will become    ． A. too anxious to relax.               B. unable to stay still. C. unable to have real rest.             D. excited to forget sleep. 73. What we can learn from the sixth paragraph is that    ． A. more teens know how to make technology serve them B. teens used to be taught how to use technology C. we should make use of technology rather than be in the control of it D. the young generation depends less on the technology to grow up 74. According to Dr. Mary Carskadon，how to deal with the problem? A. Teenagers should judge how to use their phones. B. Teenagers should reduce their interpersonal contact. C. Teenagers should switch their phones off. D. Parents should give more attention to children's use of phones. 75．What's the passage mainly about? A. Too much phone time has a bad effect on teens' sleep. B. Too many cell phone calls have cost teens too much. C. Few cell phone calls will damage teens' friendships. D. Too little cell phone time improves teens' attention at class.