This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory Radiology, Subject name: Radiology
[{'content': 'Sandstorm appearance on Chest radiograph is characteristic of? \nSelect and explain. \nA. Pulmonary edema, B. Pulmonary alveolar proteinosis, C. Pulmonary alveolar microlithiasis, D. Pulmonary thromboembolism', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Pulmonary alveolar microlithiasis is a chronic disease characterized by widespread diffuse bilateral intraalveolar accumulation of minute calculi (microlithiasis) especially in mid and lower zones, giving characteristic sandstrom appearance on chest radiographs.', 'role': 'assistant'}]