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
Treatment of nodulocystic acne is 
Select and explain. 
A. Erythromycin, B. Teacycline, C. Isoretinonine (Retinoic acid), D. Steroids
C: Isoretinonine (Retinoic acid)
Answer: C: Isoretinonine (Retinoic acid) 
Explanation: C i.e. Isoretinonine