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': 'Freeway space is defined as: \nSelect and explain. \nA. Vertical dimension at rest - vertical dimension at occlusion, B. Vertical dimension at occlusion + vertical dimension at rest, C. Vertical dimension at rest, D. Vertical dimension at occlusion - vertical dimension at rest', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]