question: Q:A 67-year-old woman comes to the physician for chest tightness, shortness of breath, and lightheadedness. She has experienced these symptoms during the past 2 weeks while climbing stairs but feels better when she sits down. She had a cold 2 weeks ago but has otherwise been well. She appears short of breath. Her respirations are 21/min and blood pressure is 131/85 mmHg. On cardiovascular examination, a late systolic ejection murmur is heard best in the third right intercostal space. The lungs are clear to auscultation. Which of the following mechanisms is the most likely cause of this patient's current condition?? 
  {'A': 'Inflammatory constriction of the bronchioles', 'B': 'Narrowing of the coronary arterial lumen', 'C': 'Cellular injury of the esophageal epithelium', 'D': 'Critical transmural hypoperfusion of the myocardium', 'E': 'Increased left ventricular oxygen demand'},