This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Back region, Subject name: Anatomy
[{'content': 'Which veebral segment is numerically most constant? \nSelect and explain. \nA. Cervical, B. Thoracic, C. Lumbar, D. Sacral', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The number of veebrae in a region can vary but overall the number remains the same. The number of those in the cervical region however is only rarely changed.', 'role': 'assistant'}]