已知a、b、c分别为△ABC的三条边长，试说明：b²+c²-a²+2bc＞0．

The Customs surveillance zone include 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