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': 'Ability of an organism to induce clinically apparent illness is known as: \nSelect and explain. \nA. Infectivity, B. Pathogenicity, C. Virulence, D. Viability', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Infectivity: It is the ability of an infectious agent to invade and multiply in a host. Pathogenicity: It is the ability of an organism to induce clinically apparent illness. Virulence: It is the propoion of clinical cases resulting in severe clinical disease. Ref: Park, 21st Edition, Page 34.', 'role': 'assistant'}]