cf巴雷特战龙怎么获得:爱迪生经过多少次实验发明了电灯(急需)

来源:百度文库 编辑:高校问答 时间:2024/05/07 19:50:26
大约多少次?

2000多次.

6000多种材料,试验了7000多次

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