This ECG is from an asymptomatic 25 year old male with a grade 4/6 systolic murmur similar to that reproduced here. It was heard best in the 2nd and 3rd left intercostal spaces and radiated towards the neck. Note the ejection sound (ES) and the very narrowly split 2nd heart sound. Which of the following do you think is the most likely cause of the murmur and what would you estimate to be the severity of the lesion? Ventricular Septal Defect Aortic Stenosis Pulmonic Stenosis