Claire can complete spring-cleaning in a house in 5 hours. Ruth can complete spring-cleaning in the same house in 7 hours. If Claire works for 1 hour alone and then Ruth joins her to finish the cleaning, what is the total time it takes to complete spring cleaning?
()can not cause oil flow from water outlet of self-cleaning separator.
In cleaning up an oil spill, the use of straw or reclaimed paper fibers would be an example of which type of oil removal?()
() is arranged for cleaning the lubricating oil in the system and clean oil can be provided from a storage tank.
()your mother()some cleaning on Sundays?
The maintenance work for sailors includes cleaning , repairing, and ()(涂漆) work on board a ship.
()your mother()some cleaning on Sundays?
The sailors do cleaning and repair work under the supervision of the ().
Please()a cleaning gang to sweep out the hold.