Quite often, it's natural to pick x and y in a certain way, because starting a projectile near the Earth, it makes sense to pick the horizontal as x and vertical as y.
我们经常会很自然地选取 x 轴和 y 轴,因为如果在地表附近做抛物运动,我们通常以水平方向为 x 轴,竖直方向为 y 轴
Though it is still near the bottom of the UN's human-development index, it is ranked quite high for governance and freedom, coming 18th out of Africa's 53 countries.
