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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吹扫炉膛负压测点必须做的措施包括（）。

A、解除炉膛负压高低Ⅱ值灭炉保护；

B、解除炉膛负压控制自动；

C、解除送风量自动；

D、解除二次风门层操自动。