Not all ads are used to promote a product or to increase a company’s profits. Which is the following statement correct?

A．All the ads are used to promote a product or to increase a company’s profits.

B．Neither of ads are used to promote a product or to increase a company’s profits.

C．Some of ads are used to promote a product or to increase a company’s profits.

D．None of ads are used to promote a product or to increase a company’s profits.

以下哪些情况禁止动火作业（）。

A.压力容器或管道未泄压前

B.存放易燃易爆物品的容器未清洗干净前或未进行有效置换前

C.喷漆、喷砂现场

D.遇有火险异常情况未查明原因和消除前