狒).On the other hand，a nontoothy，not-so-broad-but-open-lipped smile is associated with pleasure in human babies.Somehow we seem to have taken the fright-threat sort of smile and extended it to strangers as a friendly smile.Maybe it is not as innocent as it seems.All cultures recognize a variety of mouth gestures as indications of inner emotional states.As in our own culture，however，smiles come in many varieties，not all of them interpreted as friendliness.

Frank McAndrew，professor of psychology at Knox College in Galesburg，has done extensive research on facial expressions.He answers as follows: Baring one's teeth is not always a threat.In primates，showing the teeth，especially teeth held together，is almost always a sign of submission.The human smile probably has evolved from that.In the primate threat，the lips are curled back and the teeth are apart-you are ready to bite.But if the teeth are pressed together and the lips are relaxed，then clearly you are not prepared to do any damage.These displays are combined with other facial features，such as what you do with your eyes to express a whole range of feelings.In fact，human smiling generally can express many different feelings.It can convey friendly feelings-think of people seeing long-separated friends，but it sometimes does not reflect true friendly feelings-think of politicians smiling for photographers.What is especially interesting is that you do not have to learn to do any of this-it is natural behavior.Kids who are born blind never see anybody smile，but they show the same kinds of smiles in the same situations as sighted people.

【语篇解读】　本文为说明文。人们总是把微笑和友好等同起来，但事实却并非如此。

3.Which may Anthony Stocks agree with?

A.Human babies' tooth-baring smile shows friendship.

B.Human babies are less sensitive to threats.

C.People can clearly explain the evolution of smiles.

D.People tend to interpret all smiles as friendliness.

答案　D　[细节理解题。根据第二段中的"Somehow we seem to have taken the fright-threat sort of smile and extended it to strangers as a friendly smile...not all of