单项选择题

Passage There

A group of people who share the same interests and way of life is called a society. Sociology is the science that examines human society. The term sociology is derived from the Lation word socius, which means "companion, union of people." Sociologists are interested in how a society began and how it grew. They also study the levels within a society. For example, the child is part of the family, the family is part of the neighborhood, and the neighborhood is part of the community. There are many different groups, and sociologists are interested in the effect that these groups have on people. A Frenchman named Auguste Comte made sociology a separate science in the 1830s. He suggested that a new science was necessary to study a society of people. A famous book, Principles of Sociology, was published by and Englishman, Herbert pencer, in 1882. This book had an unprecedented effect on the science of sociology. In this book, Spencer theorized that a society’s customs evolved, or grew from very simple to more complicated and advanced. This theory shows the influence that Charles Darwin(who believed that man had evolved from very simple forms to the present human) had on Spencer.

The word "levels" in line 5 means "（）".