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: Forensic Medicine
[{'content': 'Speed ball is cocaine plus - \nSelect and explain. \nA. Heroin, B. Cannabis, C. Amphetamine, D. LSD', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A combination of heroin and cocaine is called as speed balls REF;THE SYNOPSIS OF FORENSIC MEDICINE:KS NARAYANA REDDY;28th EDITION;PAGE NO 347', 'role': 'assistant'}]