Final answer:
Ventricular Septal Defect (VSD) is the most frequently occurring congenital heart defect, which allows blood to flow between the two lower chambers of the heart leading to potential complications if untreated.
Step-by-step explanation:
The most frequently occurring congenital heart defect is the Ventricular Septal Defect (VSD). A VSD is an opening in the interventricular septum, which allows blood to flow between the heart's two lower chambers, or ventricles. This can lead to increased workload on the heart and lungs, and if left untreated, may cause congestive heart failure.
Among the options provided, the Tetralogy of Fallot is a congenital condition characterized by four heart defect components, though it is not the most common defect. The term "tetralogy" refers to the four parts of the condition, which are pulmonary infundibular stenosis, overriding aorta, ventricular septal defect, and right ventricular hypertrophy. However, a patent ductus arteriosus and atrial septal defect are also common congenital defects that present different symptoms and require various treatment approaches.