单项选择题
A.The hose should not be twisted
B.The hose should be protected with a sleeve if it is subjected to rubbing
C.There should be some slack in the hose
D.All of the above
单项选择题 A lube oil filter can be used to remove most contaminants from lube oilA contaminant which will remain in the lube oil after filtering is （）.
单项选择题 Which pump installation would require an external source of sealing water?（）
单项选择题 The accumulation of air and other non-condensable gases in a refrigeration system will （）.