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: Medicine
[{'content': 'False statement for Pyrexia of unknown origin: \nSelect and explain. \nA. Cause unknown despite more than 3 days of hospitalization, B. Cause unknown even after 3 OPD visits, C. Fever persisting after 1 month of regular treatment, D. Usually, fever more than 38.3 degree Celsius', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Fever persisting after 1 month of regular treatment PUO was defined by Petersdorf and Beeson in 1961 as 1) temperatures of more than 38.3 degree C/ 101 degree F on several occasions; 2) a duration of fever of more than 3 weeks; 3) failure to reach a diagnosis despite 1 week of inpatient investigation The new definition is broader, stipulating 3 outpatient visits or 3 days on the hospital without elucidation of a cause or 1 week of intelligent and invasive ambulatory investigation', 'role': 'assistant'}]