Passage Two
In recent years, many Americans of both sexes and various ages have become increasingly interested in improving their bodies. [29]They have become more devoted to physical fitness. Many persons have a strong desire to be more physically fit.
By nature, Americans are enthusiastic, and energetic about hobbies or pastimes. And now many of them apply this enthusiasm, optimism, and energy to running. [30]As a result, there are more running clubs to join and numerous books and magazines to read about running.
The desire for American people to be physically fit could probably be explained by a "passion" for good health. The high rate of heart attacks in the 1960s has caused an increase of interest in improving the health condition of human body. Middle-aged men especially suffer from heart attacks. Thus, they are one group strongly interested in taking more physical exercise. [31]In fact, many doctors often encourage their patients to become more physically active, especially those who have inactive jobs. It is quite interesting to note that the rate of heart attacks began to decrease between 1972 and 1974 and it is still decreasing now.
It seems that physical fitness has now become a new "love" of Americans. But will it last very long? Nobody knows. Only time will tell-or until another "new passion" comes along and takes its place.

答案解析：
29. Why are Americans so interested in physical exercise?
[D]解析：推断题。短文提到，很多美国人都致力于身体锻炼，他们对身体健康有强烈的愿望。D为原文的同义表达，故正确。
30. What happens when American people apply great enthusiasm in running?
[A]解析：听到enthusiasm... to running之后马上就是clubs，books这两个核心词，故A正确。
31. What kinds of patients are especially encouraged to take part in physical exercise?
[D]解析：细节题。文中提到，很多医生鼓励他们的病人多参加体育锻炼，特别是那些工作中不大活动的人。故D正确。