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
A patient with 14 days of fever is suspected of having typhoid; what investigation should be done: 
Select and explain. 
A. Blood culture, B. Widal, C. Stool culture, D. Urine culture
B: Widal
Answer: B: Widal 
Explanation: 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