单项选择题
The following measures can be used to improve oily water separator’s separating effect except （）
A.overhauling every two year B.working at intervals C.renewing filtration material D.pumping bilge water from different layers respectively
单项选择题 If separating effect is not good, which measure should be taken （）
单项选择题 If separating effect is not good, we can improve it by （）
单项选择题 If found oil when we open low oil level plug of separator, it indicates （）
