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
[{'content': 'Heimilch valve is used for drainage of: \nSelect and explain. \nA. Pneumothorax, B. Hemothorax, C. Empyema, D. Malignant pleural effusion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pneumothorax', 'role': 'assistant'}]