A project has the following characteristics: payback of $2,000, profit of $1,000, project cost of $800, life cycle cost of $1,200. What is the benefit cost ratio of the project

A．2.50.

B．1.25.

C．1.67.

D．0.83.

混砂车混合罐液面控制系统的作用是（）。

A.控制吸入泵

B.控制吸入阀，保持液面在设定值

C.控制排出泵

D.控制排出泵，保持液面在设定值