This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
The Heidbrink meter in Boyle&;s machine 
Select and explain. 
A. Reduces pressure of gases, B. Indicates flow of gases, C. Indicates humidity of gases, D. It a fixed orifice meter
B: Indicates flow of gases
Answer: B: Indicates flow of gases 
Explanation: Heidbrink is a flowmeter used in past. It consists of a metal tapered tube with inveed black float. The upper-end projects in the glass tube. Other type of flowmeter used in past was Connell which has round bobin.