单项选择题

When Mrs. Joseph Grudger died recently in Vienna, Austria, people asked the obvious question," why did she live to be 107" Tentative (推测性的)answers were provided by a survey conducted among148 Viennese men and women who had reached the age of 100. Somewhat surprising was the fact that the majority had lived most of their lives in cities. In spite of the city’s image as an unhealthy place, city living often provides benefits that country living can lack. One factor seems to be important to the longevity of those interviewed.
This factor is exercise. In the cities it is often faster and less frustrating to walk short distances than to wait for a bus. Even taking public transportation often requires some walking. Smaller apartment houses have no elevators, and so the people living there must climb stairs. City people can usually walk to local supermarkets. Since parking spaces are hard to find, there is often no alternative to walking.
On the other hand, those who live in the country, and suburbs do not have to walk every day. In fact, the opposite is often true. To go to school ,work, or almost anywhere else, they must ride in cars.

We can learn from this passage that（）