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     LONDON----Here’s a new warning from health experts: Sitting is deadly.
     Scientists are increasingly warning that sitting for prolonged periods — even if you also exercise regularly — could be bad for your health. And it doesn’t matter where the sitting takes place — at the office, at school, in the car or before a computer or TV — just the overall number of hours it occurs. Several studies suggest people who spend most of their days sitting are more likely to be fat, have a heart attack or even die.
　　In an editorial published this week in the British Journal of Sports Medicine, Elin EkblomBak of the Swedish School of Sport and Health Sciences suggested that authorities rethink how they define physical activity to highlight the dangers of sitting.
　　While health officials have issued guidelines recommending minimum amounts of physical activity, they haven’t suggested people try to limit how much time they spend in a seated position.
　　"After four hours of sitting, the body starts to send harmful signals," Ekblom-Bak said. She explained that genes regulating(调节) the amount of glucose（葡萄糖）and fat in the body start to shut down.
　　Even for people who exercise, spending long periods of time sitting at a desk is still harmful. Tim Armstrong, a physical activity expert at the World Health Organization, said people who exercise every day — but still spend a lot of time sitting — might get more benefit if that exercise were spread across the day, rather than in a single bout.（一回）
　　Still, in a study published last year that tracked more than 17,000 Canadians for about a dozen years, researchers found people who sat more had a higher death risk, independently of whether or not they exercised.
　　"We don’t have enough evidence yet to say how much sitting is bad," said Peter Katzmarzyk of the Pennington Biomedical Research Center in Baton Rouge, who led the Canadian study. "But it seems the more you can get up and interrupt this sedentary behavior, the better."
　　Figures from a U.S. survey in 2003-2004 found Americans spend more than half their time sitting, from working at their desks to sitting in cars.
　　Experts said more research is needed to figure out just how much sitting is dangerous, and what might be possible to offset those effects.
　　"People should keep exercising because that has a lot of benefits," Ekblom-Bak said. "But when they’re in the office, they should try to interrupt sitting as often as possible," she said.
1.What is the best title for the text?
A. Not Sitting Too Much While Working        B. How To Avoid Sitting Too Much
C. Sitting Too Much Could Be Deadly          D. More And More People Sit Too Much
2. According to the research,______________.
A. the more time you spend in exercising in a single bout, the healthier you will be.
B. those who often sit too much are sure to grow fat or suffer from a heart attack.
C. regular exercise is effective to get rid of the side effect of sitting too much.
D. you had better not sit for more than four hours in a single bout.
3. How does the danger of sitting too much affect the human body?
A. It results in a higher death risk.
B. It increases glucose and fat in the body.
C. It makes a person unable to exercise long enough in a day.
D. It causes the gene to fail to balance the glucose and fat in the body.
4. In the opinion of Ekblom-Bak, you’d better have a rest in the office by________.
A. sending your friends e-mails
B. having a walk around your office
C. chatting online or playing computer games 
D. listening to music with your head on the desk.