This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Dental
[{'content': 'Psoralen-A is used in the treatment of - \nSelect and explain. \nA. Pemphigus, B. Vitiligo, C. Pityriasis alba, D. Icthyosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Psoralen and many of its derivatives are naturally occurring tricyclic furocoumarins. The derivative most widely used in photochemotherapy is 8 - methoxypsoralen (8MOP, methoxsalen, xanthotoxin) which is principally of plant origin but it is available as a synthetic drug. 4, 5, 8-trimethyl psoralen (TMP, trioxsalen) is a synthetic compound which is less phototoxic after oral administration and is primarily used for the treatment of vitiligo. ijdvl journal of dermatology, psoralens.', 'role': 'assistant'}]