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': 'Block out done on proximal tooth surfaces to be used as guiding planes is \nSelect and explain. \nA. Parallel blockout, B. Shaped blockout, C. Arbitary blockout, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]