如果把一个体积为125立厘米的正方体铁块切割成体积相等的8个小正方体，则每个小正方体铁块的表面积是（）。

A．6.25平方厘米

B．15.625平方厘米

C．16.5平方厘米

D．37.5平方厘米

If the radio signal ground wave extends out for less distance than the minimum skywave distance，there is an area in which no signal is received．This is called the（）.

A.Skip zone

B.Blackout zone

C.Diffraction zone

D.Shadow zone