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': 'Transmission of hepatitis A virus occurs -a) One week before and one week after onset of symptomb) 2 weeks before onset of symptomsc) 2 weeks after onset of symptomsd) 1 week after onset of symptoms \nSelect and explain. \nA. c, B. d, C. bd, D. ac', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]