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在日常生活和生产劳动中,我们总会碰到各种各样的东西,细心的同志常常会提出许许多多的问题。例如;火是什么现象?水是什么物质?水为什么能灭火?铁是什么物质?铁器为什么会生锈?为什么涂上油就
In daily life and productive labor, we always encounter a wide variety of things. Attentive comrades often ask many questions. For example, what is the phenomenon of fire? What is the water? Why can the water be extinguished? What is the iron? Why does the iron rust? Why oil?