单项选择题 A simple pumping system consists of a suction branch, a pump and （）.

单项选择题 A(n) （） is a device which adds to the energy of a liquid or gas causing an increase in its pressure and a movement of the fluid.

单项选择题 Lubricating oil systems are fitted with a wide variety of strainers some of which can be cleaned in site while others have replaceable cartridgesThe bold and italic word “which” means （）.