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': 'The cohesive gold used as a bulk filler is \nSelect and explain. \nA. Electra alloy, B. Mat gold, C. spherical gold, D. gold foil', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]