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
All except one are centrally acting muscle blockers: 
Select and explain. 
A. Meprobamate, B. Baclofen, C. Diazepam, D. Dantrolene sodium
D: Dantrolene sodium
Answer: D: Dantrolene sodium 
Explanation: None