问题
单项选择题
下列数据中，（）是非线性数据结构。
A.栈
B.队列
C.完全二叉树
D.堆
答案
参考答案：C
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下列数据中，（）是非线性数据结构。
A.栈
B.队列
C.完全二叉树
D.堆
参考答案：C
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| 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 1 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 2 . Research is preliminary, but several studies 3 people who spend most of their days sitting are more likely to be fat, have a heart attack or even die. In an editorial 4 this week in the British Journal of Sports Medicine, Elin Ekblom-Bak of the Swedish School of Sport and Health Sciences suggested that authorities rethink how they define 5 activity to highlight the dangers of sitting. While health officials have issued guidelines 6 minimum amounts of physical activity, they haven't suggested people try to limit how much time they spend in a seated 7 . "After four hours of sitting, the body starts to send 8 signals," Ekblom-Bak said. She explained that genes regulating the amount of glucose and fat in the 9 start to shut down. Even for people who 10 , 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 who exercise every day- 11 still spend a lot of time sitting-might get more benefit if that exercise were spread across the day, 12 in a single bout. That wasn't 13 news for Aytekin Can, 31, who works at a London financial company, and spends most of his days sitting 14 a computer. Several evenings a week, Can also teaches jiu jitsu, a Japanese martial art 15 wrestling, and also does Thai boxing. "I'm sure there are some detrimental 16 of staying still for too long, but I hope that being 17 when I can helps," he said. "I wouldn't want to think the sitting could be 18 dangerous." Still, in a study published last year that tracked more than 17,000 Canadians for about a dozen years, researchers found people who sat 19 had a higher death risk, independently of whether or not they exercised. Figures from a US 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 20 just how much sitting is dangerous, and what might be possible to offset those effects. | ||||
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