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: Dental
[{'content': 'Gutta-percha is radio-opaque due to presence of: \nSelect and explain. \nA. Zinc oxide eugenol, B. Barium sulphate, C. Potassium sulphate, D. Barium oxide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]