阅读下列短文，从每题所给的四个选项(A、 B 、 C和D)中，选出最佳选项，并在
答题卡上将该项涂黑。
【2012陕西卷】
A
Eating too much fatty food, exercising too little and smoking can raise your future risk of heart disease. But there is another factor that can cause your heart problems more immediately: the air you breathe.
Previous studies have linked high exposure (暴露）to environmental pollution to an increased risk of heart problem, but two analyses now show that poor air quality can lead to heart attack or stroke (中风）within as little as a few hours after exposure. In one review of the research, scientists found that people exposed to high levels of pollutants (污染物）were up to 5% more likely to suffer a heart attack within days of exposure than those with
