Urbanization
Until relatively recently, the vast majority of human beings lived and died without ever seeing a city. The first city was probably founded no more than 5,500 years ago   . In fact, nearly everyone lived on farms or in tiny rural (乡村的) villages. It was not until the 20th century that Great Britain became the first urban society in history--- a society in which the majority of people live in cities and do not farm for a living.
Britain was only the beginning.       .The process of urbanization--- the migration (迁移) of  people from the countryside to the city--- was the result of modernization, which has rapidly transformed how people live and
where they live.
In 1990, fewer than 40% of Americans lived in urban areas. Today, over 82% of Americans live in cities. Only about 2% live on farms.     .
Large cities were impossible until agriculture became industrialized. Even in advanced agricultural societies. It took about ninety-five people on farms to feed five people in cities.   _    . Until modern times, those living in cities were mainly the ruling elite(精英) and the servants, laborers and professionals who served them. Cities survived by taxing farmers and were limited in size by the amount of surplus food that the rural population produced and by the ability to move this surplus from farm to city.
Over the past two centuries, the Industrial Revolution has broken this balance between the city and the country     _    Today, instead of needing ninety-five farmers to feed five city people, one American farmer is able to feed more than a hundred non-farmers.

A．That kept cities very small.

B．The rest live in small towns.

C．The effects of urban living on people should be considered.

D．Soon many other industrial nations become urban societies.

E. But even 200 years ago, only a few people could live in cities.
F. Modernization drew people to the cities and made farmers more productive.
G. Modern cities have destroyed social relations and the health of human beings.