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: Pharmacology
In which of the following categories are ephedrine, tyramine and amphetamine classified: 
Select and explain. 
A. Anticholinesterases, B. Alpha-adrenergic blocking agents, C. Indirect acting sympathomimetics, D. Direct acting sympathomimetics
C: Indirect acting sympathomimetics
Answer: C: Indirect acting sympathomimetics 
Explanation: None