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': 'In a syphilis patient, site which does not help in isolation of organism - \nSelect and explain. \nA. Gumma, B. Primary chancre, C. Mucosal patch, D. Maculopapular rash', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Demonstration of T.pallidum in gumma is very rare.', 'role': 'assistant'}]