阅读理解 Researches say people traveling in traffic are three times more likely to suf

fer 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 700 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 gasses 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(阻塞) to form. in the arteries(动脉) 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 was 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 fro cleaner vehicles and better city planning.

9.According to the study, which of the following ways is the safest in traffic？

A. Driving a car

B. Walking on the street

C. Taking a bus

D. Riding a bicycle

9.From among the 700 people who suffered heart attacks we learn that ______.

A. those who have been in traffic are three times as many as those who have not

B. those who have been in traffic for more than one hour are most likely to suffer heart attacks

C. the risk of a heart attack is three higher among those who have been in traffic than those who have not

D. Most of the subjects (实验对象) felt uncomfortable during the four days before the attack

9.The particles released from vehicles ______.

A. build up in the blood