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: Psychiatry
'Flash-back' phenomenon is seen with the use of - 
Select and explain. 
A. Cannbis, B. Psilocybin, C. LSD, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Flash-back is the spontaneous occurrence of previously experienced drug effects without taking the drug at the moment. Flash-back is usually associated with hallucinogens (LSD, Psilocybin, psilocin) and occasionally with cannabis (marijuana).