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: Forensic Medicine
Which of the following poisoning is associated with the development of Buonian line? 
Select and explain. 
A. Zinc, B. Lead, C. Arsenic, D. Mercury
B: Lead
Answer: B: Lead 
Explanation: Buonian line is a stippled bluish black line due to epithelial deposition of lead sulphide granules on the gums at the junction with the teeth. It is seen in about 50 - 70% of the cases of Lead poisoning. Lead is a typical cumulative poison. Lead poisoning occurs from the toxic effects of the following principle lead salts: Lead acetate - white crystals Lead carbonate - white crystalline powder Lead chromate - bright yellow powder Lead monoxide - pale brick-red Lead tetroxide - red lead/sindur Lead sulphide - least toxic Ref: The Essentials of Forensic Medicine And Toxicology by Dr. K. S. Narayan Reddy 27th edition; Pages 464; 475-9; 473.