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Here's a warning from health experts: Sitting is deadly. Scientists are increasingly warningthat sitting for prolonged periods--even if you also exercise regularly--could be bad for yourhealth. And it doesn't matter where the sitting takes place at the office, at school, in the car orbefore a computer or TV--just the overall number of hours it occurs.

Research is preliminary, but several studies suggest people who spend most of their dayssitting 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 Ekblom-Bakof the Swedish School of Sport and Health Sciences suggested that authorities rethink how theydefine physical activity to highlight the dangers of sitting.

While health officials have issued guidelines recommending ~nini~num amounts of physicalactivity, 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. Sheexplained that genes regulating the amount of glucose and fat in the body start to shut down.

Even for people who exercise, spending long stretches of time sitting at a desk is still harmful.Tim Armstrong, a physical activity expert at the World Health Organization, said people whoexercise every day--but still spend a lot of time sitting--might get more benefit if that exercisewere spread across the day, rather than in a single bout.

That wasn't welcome news for Aytekin Can,31, who works at a London financial company,and spends most of his days sitting in front of a computer. Several evenings a week, Can alsoteaches jiujitsu, a Japanese martial art involving wrestling, and also does Thai boxing.

"I'm sure there are some detrimental effects of staying still for too long, but I hope that beingactive when I can helps," he said. "I wouldn't want to think the sitting could be that dangerou

A.Exercising can't help reduce the harm caused by sitting
B.The harm depends on the prolonged time sitting at a desk
C.Exercising is not necessary for people
D.Exercising has no advantages for people who often sit

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答案： B

本题解析：

题干中的句子意为“即使对那些经常锻炼的人来说，长时间坐着也有害。”该句所在段讲到，世界卫生组织的身体锻炼专家蒂姆·阿姆斯特朗说，对于那些每天锻炼但依然有很多时间是处于静坐状态的人来说，如果每天的锻炼可分散进行而不是一次集中完成，效果会更好。由此可推知，久坐的危害取决于持续很长时间的坐的动作，如果锻炼时间和坐下来的时间都很集中，那么危害就很大。因此，正确答案是B。