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: Medicine
[{'content': 'Substernal pain is a feature of: \nSelect and explain. \nA. Tachycardia, B. Emphysema, C. Angina pectoris, D. Thrombi and emboli', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]