最佳答案:What's the difference between college and high school education?
最佳答案:The size of the university is only one third of my high school. This is totally
最佳答案:你可以了解一下几何光学里面得费马原理,费马原理表述为:光在指定得两点传播,实际得光程总是一个极值.在一般情况下光程大多是取极小值.由两点间直线距离最短可得光在均