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
Vitamin D analogue calcitriol is useful in the treatment of ? 
Select and explain. 
A. Lichen planus, B. Psoriasis, C. Phemphigus, D. Leprosy
B: Psoriasis
Answer: B: Psoriasis 
Explanation: Ans. is 'b' i.e., Psoriasis