Many of us sit in front of a computer for eight hours a day, and then go home and head for the couch to surf the Web or watch te

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问题     Many of us sit in front of a computer for eight hours a day, and then go home and head for the couch to surf the Web or watch television, exchanging one seat and screen for another. Even if we try to squeeze in an hour at the gym, is it enough to counteract (抵消) all that motionless sitting?
    A mounting body of evidence suggests not.
    Increasingly, research is focusing not on how much exercise people get, but how much of their time is spent in sedentary (久坐的) activity, and the harm that does.
    The latest findings, published this week in The Journal of the American College of Cardiology, indicate that the amount of leisure time spent sitting in front of a screen can have such an overwhelming, seemingly irreparable (无法弥补的) impact on one’s health that physical activity doesn’t produce much benefit.
    The study followed 4,512 middle-aged Scottish men for a little more than four years on average. It found that those who said they spent two or more leisure hours a day sitting in front of a screen were at double the risk of a heart attack or other heart events compared with those who watched less. Those who spent four or more hours of recreational time in front of a screen were 50 percent more likely to die of any cause. It didn’t matter whether the men were physically active for several hours a week — exercise didn’t reduce the risk associated with the high amount of sedentary screen time.
    The study is not the first to suggest that sedentary activities like television viewing may be harmful. A 2009 study reported that young children who watch one and a half to five and a half hours of TV a day have higher blood pressure readings than those who watch less than half an hour, even if they are thin and physically active.
    Recreational screen time has an "independent, injurious relationship" with heart and the blood vessels events and death of all causes, the paper concluded, possibly because it induces metabolic (新 陈代谢) changes.
    The study focused on recreational screen time because it’s the easiest to reduce, Dr. Stamatakis said. But he encouraged employees who work at computers all day to get up and take breaks and short walks periodically.
Why leisure time spent in front of the screen is related to heart diseases?

选项 A、Some content of the TV programs makes the heart beat faster.
B、It causes chemical processes in people’s body to change.
C、Extended sitting slows circulating blood to the heart.
D、Radiation from the screen causes physical harm to the heart.

答案B

解析 根据题干中的related和heart diseases将本题出处定位到第七段。该段提到,该研究报告得出结论,坐在屏幕前的娱乐时间与心血管事件及各种原因所导致的死亡之间具有“独立而有害的关系”,这很可能是因为它会引起新陈代谢变化,[B]正是对原因的同义转述,故答案为[B]。其余三个选项在文中均未提及。
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