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
[{'content': 'The Heidbrink meter in Boyle&;s machine \nSelect and explain. \nA. Reduces pressure of gases, B. Indicates flow of gases, C. Indicates humidity of gases, D. It a fixed orifice meter', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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.', 'role': 'assistant'}]