单项选择题
Distilled water from an evaporator may be discharged into a potable water tank （）.
A.through a detachable hose connection B.after passing through an activated charcoal filter C.after chemical analysis shows it is fit for consumption D.through a solenoid operated three-way valve
单项选择题 If a centrifugal pump vibrates and is noisy when operating, the cause could be （）.
单项选择题 Which of the devices listed is common to all types of pumps?（）
单项选择题 A centrifugal pump may fail to deliver water when first started if the （）.
