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': 'A 8-year old boy presented with swelling on both\nsides of the face, below the ears of 4 days duration.\nIt first started on the left side and then 3 days \nlater on the right side\n\nImmunization to this disease can be achieved by the following vaccination \nSelect and explain. \nA. MMR, B. BCG, C. Hepatitis B, D. Polio', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]