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: Medicine
Occupational exposure which is yet NOT confirmed on causing a lung problem: March 2013 
Select and explain. 
A. Nickel, B. Chromium, C. Lead, D. Arsenic
C: Lead
Answer: C: Lead 
Explanation: Ans. C i.e. Lead