This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'The adjuvant used in DPT vaccine is - \nSelect and explain. \nA. A1, B. Mg, C. Zn, D. Formaldehyde', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Adsorption of DPT vaccine on a mineral carrier like aluminium phosphate or hydroxide increases the immunological effectiveness of vaccine. Ref:PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 23rd edition , Page :162', 'role': 'assistant'}]