According to sociologists(社会学家), every modern industrial society has some form of social stratification(阶层). Class, power and status are important in deciding people’s rank in society.
Class means a person’s economic position in society. A commonly used classification is lower class, middle class and upper class. While sociologists disagree on how these terms should be exactly defined, they do describe societies like the United States quite well. One study shows that 53% of Americans belong to the lower class, 46% the middle class, and 1% the upper class. Interestingly, a surgeon earning ＄500,000 a year and a bus driver earning ＄50,000 a year both regard themselves as the middle class!
Power refers to the amount of control a person has over other people. Obviously, people in positions of great power (such as governors) exercise(行使)big power, but people who take orders from others have less power. Power and class do not always go hand in hand, however. For example, the governor of a state has great power, but he or she may not belong to a corresponding (相应的)economic class. Generally, however, there is a relationship between power and class.   
To our knowledge, there aren’t too many people who aren’t millionaires in the U.S. Senate!
Status is the honor or respect attached to a person’s position in society. It can also be affected by power and class, but not necessarily so. For example, a university professor may have a high status but not belong to a high social class or have a lot of power over others.
What can we learn about “the middle class” from Paragraph 2?

A．People earning ＄50,000 a year belong to the middle class.

B．Nearly half Americans belong to the middle class.

C．People generally consider bus drivers as the middle class.

D．Sociologists have a clear definition of the middle class.

According to the text, we know that _____.

A．power and class do not always correspond with each other

B．status refers to a person’s economic position in society

C．people with high status have a lot of control over others

D．class is less important in deciding a person’s social rank

Which of the following shows the structure of the whole text?