This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Non synthetic alkaloid compound acting similar to amphetamine is: 
Select and explain. 
A. Caffeine, B. Cocaine, C. Nicotine, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: All the above given drug are non synthetic and are CNS stimulants. REF: KD TRIPATHI 8TH ED.