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: Anaesthesia
True about Boyle's apparatus: 
Select and explain. 
A. Continuous flow machine, B. Liquid anesthetic vapours not used, C. Resistance very high, D. All
A: Continuous flow machine
Answer: A: Continuous flow machine 
Explanation: A i.e. Continuous flow machine