The authors of both studies stress that these risks are relatively small for healthy people and certainlymodest compared with other risk factors such as smoking and high blood pressure. However, it is important to be aware of these dangers because everyone is exposed to air pollution regardless of lifestyle choices. So stricter regulation by the EPA of pollutants may not only improve environmental air quality but could also become necessary to protect public health.

1. The text mainly discusses the relationship between¡¡¡¡¡¡.¡¡

A. heart problems and air quality¡¡¡¡¡¡¡¡B. heart problems and exercising

C. heart problems and smoking¡¡¡¡¡¡¡¡¡¡D. heart problems and fatty food

2. The underlined word“modest”in Paragraph 3 most probably means¡¡¡¡¡¡.¡¡

A. relatively high¡¡¡¡B. extremely low     C. relatively low¡¡¡¡D. extremely high