【四六级考试网 - 大学英语四六级考试(CET)试题】：
38. Sound personal health choice is often difficult to make because

 

　　A) current medical knowledge is still insufficient

　　B) there are many factors influencing our decisions

　　C) few people are willing to trade the quality of life for the quantity of life

　　D) people are usually influenced by the behavior of their friends

　　39. To knowingly allow oneself to pursue unhealthy habits is compared by Fries and Crapo to

　　A) improving the quality of one's life

　　B) limiting one's personal health choice

　　C) deliberately ending one's life

　　D) breaking the rules of social behavior

　　40. According to Fries and Crapo sound health choices should be based on

　　A) personal decisions B) society's laws

　　C) statistical evidence D) friends' opinions