A cow walks towards the west,then it turns to the north at 90 degrees.问题补充里)

问题描述:

A cow walks towards the west,then it turns to the north at 90 degrees.问题补充里)
Do you know in which direction the cow's tail is now?
A.West B.south C.East D.Down
我知道这题答案选D.Down,可是为什么选D?

因为牛的尾巴永远是向下的哈.