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
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 
Select and explain. 
A. ac, B. ad, C. abe, D. ade
C: abe
Answer: C: abe 
Explanation: None