**Core Concept**
Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four classic features: ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. TOF is the most common cyanotic congenital heart defect, resulting from abnormal development of the embryonic heart.

**Why the Correct Answer is Right**
The correct answer will be one of the options listed below. TOF is caused by a combination of genetic and environmental factors during embryonic development. The VSD allows blood to flow from the left to the right ventricle, while the pulmonary stenosis restricts blood flow from the right ventricle to the lungs. This leads to increased blood flow through the aorta, resulting in right ventricular hypertrophy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because TOF is indeed characterized by a large VSD, which allows blood to flow from the left to the right ventricle.
**Option B:** This option is incorrect because TOF is indeed associated with pulmonary stenosis, which restricts blood flow from the right ventricle to the lungs.
**Option C:** This option is incorrect because TOF is indeed associated with right ventricular hypertrophy, which results from increased blood flow through the aorta.

**Clinical Pearl / High-Yield Fact**
TOF is often associated with other congenital anomalies, such as atrial septal defects and patent ductus arteriosus. A classic clinical finding in TOF is the "square root of time" sign, which refers to the increasing cyanosis and oxygen saturation with age.

**Correct Answer:** A.