номер 10, страница 30 - гдз по английскому языку 8 класс рабочая тетрадь Вербицкая, Уайт

Track four.

Why are typical teenagers never tired at eleven p.m., but they hate getting up in the morning? Are they lazy? No. The good news is that it's natural. Everyone has a natural body clock, which tells them when to wake up and fall asleep. In teenagers, the chemical that controls sleep, melatonin, is in their brains between eleven p.m. and eight a.m.

The result is that teenagers don't feel tired late in the evening, but when they get up before eight a.m., their brain is telling them to sleep. This lack of sleep means they are often unhappy, angry, can't learn, and get bad marks.

In the US, a lot of high schools start at about seven thirty in the morning. This means the students are at their desks after only five or six hours sleep. However, they need nine to ten hours, because their bodies and brains are still developing, so they are very tired. Tiredness means twenty percent of high school students fall asleep during their first two hours of school.

Sleep scientists are researching the problem. They say that it is crazy to fight nature, so the only answer is for schools to start later. As one scientist said, at seven thirty a.m., students are at their desks, but their brains are at home in bed. Luckily, some head teachers listen to the new scientific advice and changed their school hours. The results are very interesting. Teachers and parents say students behave better, learn more, get better marks, and fewer students drop out.