Since the Social Classes in the United States Do Not

Since the social classes in the United States do not have any clear boundaries, how is a sociologist supposed to determine whether their subjects are in the upper class or the upper-middle class?

A) Upper class is often defined as having control over one's life and the lives of people around you, while the upper-middle class is often defined as having control only over one's own life.
B) The upper class is split into "old money" and "new money" people, while the upper-middle class simply struggles to maintain its wealth.
C) All upper class people enjoy opera and have been bred for their stations while the upper-middle class consists mostly of newly wealthy people who may not have had the same kind of upbringing.
D) In the upper class, everyone knows everyone, but in the upper-middle class, the people do not comingle.