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
Directly acting cough suppressant is : 
Select and explain. 
A. Dextromethorphan, B. Bromhexine, C. Actyl cysteine, D. Carbapentate
A: Dextromethorphan
Answer: A: Dextromethorphan 
Explanation: None