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The outer surface is plated with copper, and the raw material of the core wire is mainly aluminum. The outer surface is scraped and the aluminum core is silvery white. The quotation per unit of aluminum is about 1/4 of that of copper, and the same volume of aluminum is only 1/3 of that of copper, so the quotation per unit of copper clad aluminum is much cheaper than that of oxygen-free copper. Copper-clad aluminum has poor oxidation resistance, faster oxidation speed in humid environment, and poor tortuosity resistance of aluminum raw materials. It is not suitable for laying in the wall, and is only suitable for customers who do not have high demand for network stability or may temporarily establish a network.Third, practice deliberately and turn good speech rules into habits.一部黑人歌舞音乐片，关于大萧条时期南方一家非法经营的酒吧。这样的旗帜是有好处的，主要是用来与赵文华那样的旗帜对冲。珊瑚忙道：我自己来。