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: Dental
Which of the following anesthetic agent is frequently
used for conscious sedation? 
Select and explain. 
A. Nitrous oxide and oxygen, B. Chloral hydrate, C. Diazepam, D. Ether
A: Nitrous oxide and oxygen
Answer: A: Nitrous oxide and oxygen 
Explanation: None