They will arrive _______ Guangzhou _______ the ninth of July.

A．at, at

B．in, in

C．in, on

D．to, on

钢心铝绞线在通过交流电时，由于交流电的集肤效应，电流实际只从铝线中流过，故其有效截面积只是铝线部分面积。