单项选择题

There are many stereotypes (定型) about the character of people in various parts of the USA. In the Northeast and Midwest, people are said to be closed and private (秘密的). In the South and West, however, they are often thought of as being more hospitable (好客). Ask someone from St. Nouis where the nearest sandwich shop is, and he or she will politely give you directions. A New Yorker might eye you at first and after deciding it is safe to talk to you, might give you a rather un- expected explanation. A person from Georgia might be very king about directing you and even suggest some different places to eat. A Texan just might take you to the place and treat you to lunch.
American stereotypes are abundant. New Englanders are often thought of as being friendly and United States are often considered very outgoing. These differences in character can be traced to different factors such as climate, living conditions and historical development.
When traveling from place to place, Americans themselves are often surprised at differing degrees of friendliness in the United States.

The main idea of the passage is()

A. even Americans are surprised at the big differences among themselves
B. there are many differences in character in different parts of the USA
C. there are many reasons for the differences
D. stereotypes about people are not necessarily true