This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'All have incubatory carriers, except- \nSelect and explain. \nA. Tetanus, B. Measles, C. Whooping cough, D. Polio', 'role': 'user'}, {'content': "Answer: A \nExplanation: Tetanus is not transmitted from person to person; it has NO period of communicability. Delayed infections(up to several months later) are due to dormant spores in the wound. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 339, 340", 'role': 'assistant'}]