In a clinical study of tetralogy of Fallot, patients are examined before surgery to determine predictors observed onechocardiography that correlate with the severity of the disease and the need for more careful monitoring. A subs et of patients is found to have more severe congestive heart failure, poor exercise tolerance, and decreased arterial oxygen saturation levels. Which of the following is most likely to predict a worse clinical presentation for these patients? (A) Size of the left ventricle (B) Degree of pulmonary stenosis (C) Size of the ventricular septal defect (D) Diameter of the tricuspid valve (E) Presence of an atrial septal defect