Facial expressions carry meaning that is determined by situations and relationships. For example, in American culture  the smile is in general an expression of pleasure. Yet it also has other uses. A woman's smile at a police officer does not carry the same meaning as the smile she gives to a young child. A smile may show love or politeness. It can also hide true feelings. It often causes confusion across cultures. For example, many people in Russia smiling at strangers in public to be unusual and even improper. Yet many Americans smile freely at strangers in public places (although this is less common in big cities). Some Russians believe that Americans smile in the wrong places; some Americans believe that Russians don't smile enough. In Southeast Asian culture, a smile is frequently used to cover painful feelings. Vietnamese people may tell a sad story but end the story with a smile. Our faces show emotions, but we should not attempt to "read" people from another culture as we would "read" someone from our own culture. The fact that members of one culture do not express their emotions as openly as do members of another does not mean that they do not experience emotions. Rather, there are cultural differences in the amount of facial expressions permitted. For example, in public and in formal situations many Japanese do not show their emotions as freely as Americans do. When with friends, Japanese and Americans seem to show their emotions similarly. It is difficult to generalize about Americans and facial expressiveness because of personal and cultural differences in the United States. People from certain cultural backgrounds in the United States seem to be more facially expressive than others. The key is to try not to judge people whose ways of showing emotion are different. If we judge according to our own cultural habits, we may make the mistake of  "reading" the other person incorrectly. The author mentions the smile of the Vietnamese to prove that smile can   _   .
show friendliness to strangers. be used to hide true feelings . be used in the wrong places. show personal habits.