单项选择题
There are many stereotypes about the character of people in various parts of the United States. In the Northeast and Midwest, people are said to be closed and private. In the South and West, however, they are often thought of as being more open and hospitable. Ask someone from St. Louis 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 unexpected explanation. A person from Georgia might be very kind 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.
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 reason for the differences
D. stereotypes about people are not necessarily true