This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
The hea to the activated sludge process is ? 
Select and explain. 
A. Primary sedimentation tank, B. Sludge digester, C. Aeration tank, D. Final settling tank
C: Aeration tank
Answer: C: Aeration tank 
Explanation: Ans. is 'c' i.e., Aeration tank o The hea of the activated sludge process is aeration tank.