Before denitrification can take place, there must be presence of food (BOD), absence of oxygen, and presence of nitrate.

Before denitrification can take place, there must be presence of food (BOD), absence of oxygen, and presence of nitrate.

• A. Presence of food (BOD), absence of oxygen, and presence of nitrate.
• B. Absence of food (BOD), presence of oxygen, and absence of nitrate.
• C. Absence of oxygen, absence of nitrate, and presence of BOD.
• D. Presence of nitrate, presence of oxygen, and absence of BOD.

Answer: (A)