Nitrogen cycle of sewage, is____________________?
(A) Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
(B) Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
(C) Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
(D) Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates

