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: Radiology
[{'content': 'Which of the following best represents the bone loss in the following radiograph? \nSelect and explain. \nA. X - 1.5 mm, B. X - 0.5 mm, C. X  + 0.5 mm, D. X', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]