This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Pathology
The dangerous paicle size causing pneumoconiosis varies from - 
Select and explain. 
A. 100-150 m, B. 50-100 m, C. 10-50 m, D. 1-5 m
D: 1-5 m
Answer: D: 1-5 m 
Explanation: Ref:Textbook of pathology (Harsh Mohan)6th edition, page no.487 In general, most of the inhaled dust paicles larger than 5 mm reach the terminal airways where they are ingested byalveolar macrophages. Most of these too are eliminated by expectoration but the remaining accumulate in alveolar tissue. Of paicular interest are the paicles smaller than 1 mm which are deposited in the alveoli most efficiently. Most of the dust-laden macrophages accumulated in the alveoli die leaving the dust, around which fibrous tissue is formed. Some macrophages enter the lymphatics and reach regional lymph nodes.