The simple explanation is that in order to get down a slope one must first get up it, which was far from easy before the advent of the ski lift.
（简单的解释是为了下坡，人必须先上坡，在没有吊椅出现之前没有那么简单）。
2
Imitation marble door lift anti-skid treatment is generally applicable to the stairs, moisture and slope surface.
仿大理石电梯门套防滑处理一般适用于楼梯台阶、潮湿处和斜坡表面。
3
The results show that the flying qualities are most sensitive to variations of the longitudinal control effectiveness and the moment of inertia besides a little to variation of the lift curve slope.