This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of Skin, Subject name: Skin
Substance common in skin, hair and nail is? 
Select and explain. 
A. Vimentin, B. Keratin, C. Laminin, D. Nectin
B: Keratin
Answer: B: Keratin 
Explanation: Ans. (b) KeratinRef.: Bolognia dermatology ch: 55