在下列说法中，正确的是[ ]

A．如果两个三角形全等，则它们必是关于直线成轴对称的图形

B．如果两个三角形关于某直线成轴对称，那么它们是全等三角形

C．等腰三角形的对称轴是底边中线.

D．一条线段是关于经过该线段中点的直线成轴对称的图形

The goods, which are carried into and out of the territory by the same vessel or aircraft, are defined as______

A．transit goods
B．transshipment goods
C．through goods
D．import and export goods