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: Unknown
[{'content': 'True regarding double blinding placebo controlled clinical trial: \nSelect and explain. \nA. Some patients are not treated, B. The clinician does not know which treatment is given to the patient, C. 50% of the patients do not know what drug they receive, D. Everybody receives both the drugs', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (Refer: K. Park’s Textbook of Preventive and Social medicine, 24th edition, pg no: 78)\nBias\n\nAny systematic error in an epidemiological study occurring during data collection, compilation, analysis and interpretation\nTypes of bias', 'role': 'assistant'}]