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: Social & Preventive Medicine
Silicosis caused by ? 
Select and explain. 
A. Gold, B. Coal, C. CO, D. Silica
D: Silica
Answer: D: Silica 
Explanation: Ans. is 'd' i.e., Silica