The Customs surveillance zone include the following places except ______.
A．any seaport, railway and high way station, airport, border pass or international postal matter exchange where there is a Customs establishment
B．any place where Customs control is conducted
C．any place without a Customs establishment but which has been approved by the state council as a point of entry and exit
D．any place along the border of the country
对此二叉树中序遍历的结果为______。