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: Skin
Casal's paint necklace is caused by: 
Select and explain. 
A. Lichen planus, B. Pellagra, C. Pernicious anemia, D. SLE
B: Pellagra
Answer: B: Pellagra 
Explanation: B i.e. Pellagra