单项选择题 For a purifier, changing to a gravity disc with larger hole diameter will move the interface towards the （）.

单项选择题 For many years marine centrifuges were designed for （） operation, that is the machines were run for a period during which solids accumulated in the bowlThe machine was stopped when the accumulated solids began to impair its performance.

单项选择题 When a clarifier is running the impurities and water collect at the bowl （）.