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: Pharmacology
[{'content': 'Isotretinoin is : a) A vitamin A analogue b) Used in cystic acne c) Safe in pregnancy d) Used in psoriasis e) Bony hyperostosis is a safe effect \nSelect and explain. \nA. ac, B. ad, C. abe, D. ade', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]