Researchers say people traveling in traffic are three times more likely to suffer a heart attack. They say the risk of a heart a

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问题     Researchers say people traveling in traffic are three times more likely to suffer a heart attack. They say the risk of a heart attack is greatest within an hour of being in traffic.
    The findings are based on a German study of almost seven hundred people who suffered heart attacks. The patients described their activities during the four days before their heart attack. Researchers found that those who had been in traffic were three times more likely to have a heart attack within one hour, compared to those who had not been in traffic. Most of those in the study had been traveling by car. But some had been on bicycles and others were on buses.
    Research shows that people in cars and buses are exposed to ten times the amount of pollutants as people walking on the street. That is largely because they breathe in the particles and gases released from the vehicles in front of them. Over time, these small particles speed the buildup of a sticky substance in the blood. This can cause blockages to form in the arteries around the heart and lead to a heart attack.
    Other studies have also linked heart trouble to stress, similar to the kind that people face while driving in heavy traffic. But the researchers of the latest study say they do not know whether the increased heart attack risk is the result of stress or pollution. They suggest it may be a combination of stress, noise and pollution. Experts say the research shows the need for cleaner vehicles and better city planning to lower the risk of heart attack.
The particles released from vehicles______.

选项 A、cause high blood pressure
B、make the blood stickier
C、become blocked in the arteries
D、do little harm to the heart

答案B

解析 文章第三段第二句中指出,他们吸人了前面车辆排出的微粒和气体。第三句接着指出,时间长了,这些微粒在血液中加速堆积成黏稠物质。选项B)是对原文的同义转述,因此确定B)为本题的答案。
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