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1. |
How the performance of the rapid sand filter can be improved? |
A. | Replacing the top 15 cm layer of sand with Anthracite |
B. | Replacing the bottom15 cm layer of sand with Anthracite |
C. | Increasing the thickness of a layer of sand |
D. | Replacing 15 cm layer of Anthracite with sand |
Answer» B. Replacing the bottom15 cm layer of sand with Anthracite | |