D
If you want to live longer and lower the risk of heart disease, a move to the mountains may help． Research by scientists in Greece shows that living in the mountains is good for the heart and longevity． People living at higher altitude have lower possibility of dying from heart disease than those closer to sea level, even if they have factors that could increase their risk．"Residence in mountainous areas seems to have a 'protective effect' from heart disease," said Dr Nikos Baibas of the University of Athens．He and his colleagues suspect that the increased exercise from walking up mountainous area gives the heart a good workout and enables it to cope with lower levels of oxygen．
Researchers studied the health records and death rates of 1,150 Greeks who lived in three villages near Athens over 15 years．One village was 1,000 metres above sea level and the other two were in low-lying areas．Although men and women living in the mountainous village had higher blood pressure rates and other risk factors than people in the other villages, they had a lower rate of death from heart disease and other causes after a fifteen year follow-up．"The contrast was more evident among men than among women," Baibas added in a report in the Journal of Epidemiology and Community Health．Heart disease is one of the world's top killers．Smoking, high blood pressure, raised cholesterol levels, being overweight or obese and a family history of the illness increase the odds of developing the disease．
68．The first sentence in the passage is used to __________．
A．tell readers what the passage focuses on      
B．give a very good guessing
C．warn people of the risk of heart disease      
D．name a new unknown illness
69．According to the passage, a person _________ may have less possibility of having heart attack.
A．with more money                        B．with a better living habit
C．from higher altitude                     D．in a happier mood
70．How long does the research of the Greeks last?
A．At most 10 years．                          B．About 15 years．
C．More than 20 years．                      D．Not mentioned．
71．Apart from altitude, how many factors raise the chance of developing heart disease?
A．three                B．Four                  C．Five                 D．Six