This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following is/are the source/sources of H2S in the environment? \nSelect and explain. \nA. Coral pits & Sewers, B. Sewers, C. Coral pits & volcanic eruptions, D. Coral pits, Sewers & Volcanic eruptions', 'role': 'user'}, {'content': "Answer: D \nExplanation: H2S is formed during coke production, viscose rayon production, wastewater treatment plants, wood pulp production using the sulphate method, extraction process, oil refining and in the tanning industry. Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 794", 'role': 'assistant'}]