This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: parasitology, Subject name: Microbiology
[{'content': 'In formal ether concentration technique, which layer contain parasites - \nSelect and explain. \nA. Ether, B. Fecal debris, C. Formal water, D. Sediment', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]