Read the following paragraph carefully and select the best topic sentence from the fou

Perhaps the most startling theory to come out of kinesics, the study of body movement, was suggested by Professor Birdwhistell.He believes that physical appearance is often culturally programmed.In other words, we learn our books, but we are not born with them.A baby has generally unformed facial features.A baby, according to Birdwhistell, learns where to set the eyebrows by looking at those around family and friends.This helps explain why the people of some regions of the United States look so much alike.New Englanders or Southerners have certain common facial characteristics that cannot be explained by genetics.The exact shape of the mouth is not set at birth;it is learned after.In fact, the final mouth shape is not formed until well after permanent teeth are set.For many, this can be well in adolescence.A husband and wife together for a long time often come to look somewhat alike.We learn our looks from those around us.This is perhaps why in a single country there are areas where people smile more than those in other areas.In the United States, for example, the South is the part of the country where the people smile more frequently.In New England they smile less, and in the western part of New York state still less.Many Southerners find cities such as New York cold and unfriendly, partly because people on Madison Avenue smile less than people on Peachtree Street in Atlanta, Georgia.People in densely populated urban areas also tend to smile and greet each other in public less than do people in rural areas and small towns.()

A.Ray Birdwhistell can tell what region of the United States a person is form. by how much he or she smiles

B.Ray Birdwhistell is a leader in the field of kinesics

C.Ray Birdwhistell says that our physical appearance is influenced by the appearance of people around us

D.People who live in the country are more friendly than people who live in densely populated areas