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
Mucosa is involved in: 
Select and explain. 
A. Psoriasis, B. Lichen planus, C. Alopecia, D. Scabies
B: Lichen planus
Answer: B: Lichen planus 
Explanation: B i.e., Lichen planus