A 45 old executive who is heavy smoker, had severe retrosternal discomfort while going to toitel at 7.00 am. ECG done immediately showed ST segment elevation in inferior leads which normalised within an hour.The most likely diagnosis is -

• A. Acute myocardial infarction
• B. Prinzemental's angina
• C. Acute pericarditis
• D. Both A and B