题目

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 consider smiling at strangers in public to be unusual and even improper. Yet many Americans smile freely at strangers in public places (a过去，山区公路多为“之”字形盘山公路。现在，兴建高速公路则是逢山开道，遇沟建桥， 尽量取最短距离 （如图）。下列关于公路建设的叙述，正确的有（ ）①平原地区的地形对公路选线限制 相对山区较小；②山区修筑公路因就地取材，建设费用较少；③早期山区公路常建造成“之”字形，主要原因是为了降低线路坡度；④现在在山区兴建高速公路不呈“之”字形，主要原因为节省投资A．①③ B．②③ C．②④ D．①④