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: Orthopaedics
[{'content': 'After an operation on femur bone, chest x-ray shows widespread mottling throughout the lung field like a snowstorm, the likely cause \nSelect and explain. \nA. Air embolism, B. Bacterial pneumonitis, C. Fat embolism, D. Pulmonary embolism', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]