Cleaning is done by________________?_x005F_x000D_1) scraping and removal in filters slow sand_x005F_x000D_2) back washing in slow sand filters_x005F_x000D_3) scraping and removal in filters rapid sand_x005F_x000D_4) back washing in rapid sand filters_x005F_x000D_The correct answer is

Cleaning is done by________________?_x005F_x000D_1) scraping and remov

1.	Cleaning is done by________________?_x005F_x000D_1) scraping and removal in filters slow sand_x005F_x000D_2) back washing in slow sand filters_x005F_x000D_3) scraping and removal in filters rapid sand_x005F_x000D_4) back washing in rapid sand filters_x005F_x000D_The correct answer is
A.	(1) and (2)
B.	(2) and (3)
C.	(1) and (4)
D.	(2) and (4)
Answer» D. (2) and (4)