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': 'The person, animal, object or substance from which an infectious substance passes or is disseminated by host is called - \nSelect and explain. \nA. Reservoir, B. Source, C. Carrier, D. Homologous reservoir', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]