Body language is of great importance to humans. We carry many of the meanings through body movements. However, many forms of body language we consider to be fine in our country can get us into trouble in other parts of the world.
A smile is one of the most common examples in different countries. While Americans smile freely at strangers, in Russia this is considered strange and even impolite. In Asian countries a smile isn't necessarily an expression of joy but it can be used to express pain.
The acceptable physical distance is another major difference. In Latin America and the Middle East the acceptable distance is much shorter than what most Europeans and Americans feel comfortable with. Hand and arm movements as a form of body language are also very different among countries. Handshakes are usually acceptable almost everywhere, even between strangers; however, kissing on the cheek and touching on the shoulder or other body parts aren't. For many people in Asia and other parts of the world, such actions are seen as a violation （侵犯）of one' s personal space. This is why you should not touch others easily.
Eye contact（目光接触）is one of the forms of body language where the differences are most striking. In America and Latin America looking the other person in the eye is a sign of respect. But in Asian countries, prolonged（过长的）eye contact is especially rude, so you should try your best not to do that.
In which place is smiling at strangers considered impolite?（ ）
事实细节题。由第二段第二句可知，在美国即使对陌生人也可以不拘束地微笑，但是在俄罗斯这种表现是很奇怪的，甚至是不礼貌的。故D正确。
把10gMgCl2和MgSO4的混合物溶于适量水中，滴加2mol／L的BaCl2溶液至沉淀完全，共消耗BaCl2溶液25mL。求混合物中MgCl2和MgSO4的质量各是多少克
固定在匀强磁场中的正方形导线框abcd，各边长为1．其中ab是一段电阻为R的均匀电阻丝，其余3边均为电阻可忽略的铜线。磁场的磁感应强度为B，方向垂直纸面向里。现有一与ab段的材料、粗细、长度都相同的电阻丝PQ架在导体框上，如图所示。PQ以恒定速度方向如何
一小物块以速度v0=10m／s沿光滑地面滑行，然后沿光滑曲面上升到顶部水平的高台上，并由高台上飞出，如图所示。问当高台的高度h多大时，小物块飞行的水平距离最大这个距离是多少(g=10m／s2)
某晶体盐的水溶液呈浅绿色，在此溶液中通入氯气，溶液变为棕黄色，把所得棕黄色溶液分成两份：一份加入KSCN溶液，溶液变深红色；另一份加入BaCl2溶液，产生不溶于稀HNO3的白色沉淀，则该晶体盐的化学式是_______。
欲除去乙烷中的乙烯，可将混合气体通过盛有_______的洗气瓶；欲除去乙炔中的硫化氢，可将混合气体通过盛有_______的洗气瓶。
浓硝酸常盛装在棕色瓶中，且贮放在冷暗处，原因是_______，
碳酸氢钠溶液和烧碱溶液反应的离子方程式为_______。
常温下，氨水中存在的离子有_______。
在酸或碱存在的条件下，甲酸甲酯跟水发生水解反应的化学方程式为_______。
有下列几种气体：H2、O2、HCl、NO、NH3、CH4，其中通常情况下能用来和水做“喷泉”实验的是_______。
