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': 'In a double blind clinical drug trial \nSelect and explain. \nA. Each patient receives a placebo, B. Each patient receives both (double) treatments, C. The patients do not know which treatment they are receiving, D. The patients do not know that they are in a drug trial', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]