This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Pharmacology
Which of the following general anaesthetics has poor muscle relaxant action? 
Select and explain. 
A. Ether, B. Nitrous oxide, C. Halothane, D. Isoflurane
B: Nitrous oxide
Answer: B: Nitrous oxide 
Explanation: (Ref: KDT 6/e p371) Nitrous oxide is not a complete anaesthetic (MAC 104%). It is a good analgesic but poor muscle relaxant.