单项选择题

Faces, like fingerprints, are not the same as one another. Did you ever wonder how it is possible for us to recognize people Even a skilled writer probably could not describe all the characters that make one face different from another. Yet a very young child--even an animal, such as a bird--can learn to recognize faces. We all take this ability for granted.
We also tell people apart by how they behave. When we talk about someone’s personality, we mean the ways in which he or she acts, speaks, thinks, and feels that make him different from others.
Like the human face, human personality is very complex. But describing someone’ s personality in words is somewhat easier than describing his face. If you were asked ’to describe what a "nice face" looks like, you would have a difficult time doing so. But if you were asked to describe a "nice per son", you might begin to think about someone who was kind, thoughtful, friendly, warm. And so on.
There are many words to describe how a person thinks, feels, and acts. Gordon Allport, a U.S. scientist who studies the mind and particular person, found nearly 18,000 English words characterizing differences in person’ s behavior. And many of us use this information as a standard for describing or typing a person, bookworms, fools, hard-working types--people are described with such term.

What is the main idea of the passage()

A.It is difficult to tell someone's personality.
B.It is difficult to describe someone's face.
C.It is difficult to recognize fingerprints.
D.It is difficult to know what someone else thinks about.