The computer was used in teaching.As a result，not only ________，but students became more interested in the lessons.

A．saved was teachers' energy

B．was teachers' energy saved

C．teachers' energy was saved

D．was saved teachers' energy

生产的火灾危险性分类要分析整个生产过程中的每个环节引起火灾的可能性，生产的火灾危险性分类按其中（）的物质确定。

A．较安全 

B．较危险 

C．最安全 

D．最危险