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
A 17 year old girl had been taking a drug for the treatment of acne for the last 2 years, which has lead to pigmentation. Which drug could it be? 
Select and explain. 
A. Doxycycline, B. Minocycline, C. Azithromycin, D. Chlorpromazine
B: Minocycline
Answer: B: Minocycline 
Explanation: Both minocycline as well as chlorpromazine can cause pigmentation on long-term use.
However, as the patient in question is being treated for acne, the answer should be minocycline. Antibiotics used in acne are erythromycin, clindamycin, tetracycline, doxycycline and minocycline.