开放作文。

     请根据下面提示，写一篇短文。词数不少于50。

     In your spoken English class, your teacher shows you the following picture. You are asked to describe

the picture and explain how you understand it.

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钢是指以铁为主要元素，含碳量一般在（）以下，并含有其它元素的可变形的铁碳合金。