In a teaching session, Atrial fibrillation is correctly explained as:

A. Acute pancreatic inflammation commonly presenting with severe epigastric pain and elevated pancreatic enzymes. B. A supraventricular arrhythmia with disorganised atrial activity and an irregularly irregular pulse. C. A chronic inflammatory airway disorder with variable and usually reversible airflow obstruction. D. A rapid severe systemic hypersensitivity reaction that may compromise airway, breathing or circulation.