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
At a flow rate of 3L/min, inspiratory (FUO2) concentration of 30–60% can be achieved by using a – 
Select and explain. 
A. Nasopharyngeal catheter, B. Simple face mask, C. Venturi mask, D. Head box
A: Nasopharyngeal catheter
Answer: A: Nasopharyngeal catheter 
Explanation: Nasopharyngeal catheter deliver 32% of O2 (FiO2 → 0.32) at flow-rate 3 litre / minute.