In a tree on a tree区别
问题描述：
In a tree on a tree区别
答
in a tree树里面,从外面看不到
on a tree树外面看到
on the tree 比in the tree较常见,但两者都是指"在树上",没啥分别；要分的话,唯有这样in the tree 是比 on the tree 隐蔽.