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According to a recent survey, British teenagers are not in good health because they don't have enough time for sleep. They don't sleep well, either. They are often disturbed(打扰) by electronic gadgets(器具，装置) in their bedrooms. We call such kind of sleep “junk sleep”.
We did a survey among 1,000 students aged 12 to 16, and we found out that 30 percent of them slept for only 4 to 7 hours a day. Nearly a quarter said they fell asleep while they were watching TV, listening to music or using other electronic gadgets.'
Nowadays, almost all the teenagers have a phone, music system or TV in his or her bedroom. Almost 20 percent of the teenager boys said the quality of their sleep were not good. It was affected by leaving their TVs or computers on. The survey also found out that 40 percent of young people felt tired every day. What's more, the girls aged 15 to 16 felt the worst among them.
“Teenagers need to realize the importance of sleeping well. If they sleep well, they will be able to study hard and perform well at school. I am shocked to know that so few teenagers have noticed the close connection between sleep and schoolwork,” said Dr Chris.
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l，则以氢气的浓度变化表示该反应在2s内的平均反应速率是
