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
Skin pigmentation resembling 'rail road tracks' seen in 
Select and explain. 
A. Marijuana, B. Opium, C. Barbiturates, D. Alcohol
B: Opium
Answer: B: Opium 
Explanation: 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