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': 'Kala azar is spread by – \nSelect and explain. \nA. House–fly, B. Black–fly, C. Sand–fly, D. Tsetse–fly', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]