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
[{'content': 'The heart to the activated sludge process is – \nSelect and explain. \nA. Primary sedimentation tank, B. Sludge digestor, C. Aeration tank, D. Final settling tank', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]