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: Microbiology
[{'content': 'A patient with 14 days of fever is suspected of having typhoid; what investigation should be done: \nSelect and explain. \nA. Blood culture, B. Widal, C. Stool culture, D. Urine culture', 'role': 'user'}, {'content': "Answer: B \nExplanation: Widal test is the investigation of choice in 3rd week. Ref: Text Book of Microbilogy By Ananthanarayan, 6th Edition, Page 275 and 8th Edition, Page 296 ; Harrison's Principles of Internal Medicine, 15th Edition, Page 972 ; Essentials of Pediatric By OP Ghai, 3rd Edition", 'role': 'assistant'}]