This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Medicine
[{'content': 'A young man repos chest pain retrosternal over last few hours. Pain is not related to . and relieved significantly on sitting and forward. Likely possibility is - \nSelect and explain. \nA. Angina pectoris, B. Acute pericarditis, C. Reflux esophagitis, D. Rib fracture', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Acute pericarditis is a type of pericarditis (inflammation of the sac surrounding the hea, the pericardium) usually lasting less than 6 weeks. It is the most common condition affecting the pericardium. Ref Davidson 23rd edition pg 525', 'role': 'assistant'}]