书面表达。

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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乳化液泵开动前应检查哪些部位？（）

A.作业环境巷道帮顶支护情况

B.润滑油的油质及油量

C.泵站各联接螺栓、联轴器和管路连接

D.开关操作手把

E.乳化液浓度