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
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 - 
Select and explain. 
A. Angina pectoris, B. Acute pericarditis, C. Reflux esophagitis, D. Rib fracture
B: Acute pericarditis
Answer: B: Acute pericarditis 
Explanation: 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