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: Social & Preventive Medicine
[{'content': 'Epidemics of Relapsing Fever are caused by: \nSelect and explain. \nA. Louse, B. Soft tick, C. Hard tick, D. Rat flea', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Louse', 'role': 'assistant'}]