This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiration, Subject name: Pathology
[{'content': 'The dangerous particle size causing pneumoconiosis varies from: \nSelect and explain. \nA. 100-150 um, B. 50-100 um, C. 10-50 um, D. 1-5 um', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) 1-5 um(Ref: Robbins 9th/pg 689; 8th/pg 697)For pneumoconiosis, the most dangerous particles are from 1 to 5 um in diameter, because particles of this size may reach the terminal small airways and air sacs and settle in their linings.', 'role': 'assistant'}]