THE DIFFERENCE BETWEEN PLANTS AND ANIMALS
Few Americans study stay put for a lifetime. They move from town to city or to suburb, from high school to college in a different state, from a job in one region to a better job elsewhere, from the home where they raise their children to the home where they plan to live after retirement. With each move they are forever making new friends, who become part of their new life at that time.
文章的开头指出了美国人很少固定生活在一个地方过一辈子，然后下文再围绕这一主题展开细节及论证。