单项选择题
（） is the production of pure water from sea water by evaporation and re-condensing.
A.Evaporation B.Circulation C.Condensation D.Distillation
单项选择题 Which of the following can be used in hydraulic transmission system?（）
单项选择题 （） play a very important part in hydraulic systems by preventing interaction between different parts of the hydraulic circuit.
单项选择题 Cargo handling unit is rated according to the （） to be lifted.
