This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Poisoning, Subject name: Anatomy
[{'content': "Skin pigmentation resembling 'rail road tracks' seen in \nSelect and explain. \nA. Marijuana, B. Opium, C. Barbiturates, D. Alcohol", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Chronic opium poisoning They have dry skin with needle puncture marks and sometimes masked by tattooing. Abscesses and thrombosed veins may be seen. I. V users may develop pigmentation and scars on front of the elbow called railroad tracks. Drug addicts may tattoo this area to mask the scars. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 489', 'role': 'assistant'}]