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': 'Which of the following is true regarding Salmonella infection - \nSelect and explain. \nA. Urine culture is + ve in 1st week, B. Stool culture is + ve in 1st week, C. Blood culture is + ve in 3-7 days, D. Widal test is + ve in 1st week', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]