美国社会阶级不像欧洲国家那样固定，加上公共教育的普及，使沿着社会阶梯向上流动成为可能。
Unlike European countries, the social classes in America is not so stable. Further more, with the advocation of public education, movements upwards along the social ladder have become possible.
她向前和向上的力量使她的双脚都离开了地面。
Her forward and upward momentum have brought both of her feet off the ground.
盐的密度低于周围的岩石，所以会向上抬升，使覆盖其上的岩层形成穹顶状。
Salt has lower density than the surrounding rock, so it tends to flow upwards, pushing up the overlying layers of rock to form a dome.
应用推荐