Bulbs/lights电灯泡Just imagine what our world would be like without lights at night.There would be no road lights,the cities will be in darkness.How would people the colourful nightlife without lights...why do you think it is the most useful invention?您好，我在“电灯”下面写的那么多都是原因啊 百度教育团队【海纳百川团】为您解答如满意，请点击“选为满意答案”按钮，谢谢～