**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 one of the most common cyanotic heart defects, resulting from abnormal development of the heart during embryogenesis.

**Why the Correct Answer is Right**
The characteristic "boot-shaped" heart on chest X-ray is a hallmark of TOF. This occurs due to the right ventricular hypertrophy, which causes the cardiac silhouette to have a distinctive contour. The X-ray may also show decreased pulmonary vascular markings, indicating decreased blood flow to the lungs due to pulmonary stenosis. In TOF, the VSD allows blood to flow from the left ventricle to the right, bypassing the pulmonary circulation, thus reducing pulmonary blood flow.

**Why Each Wrong Option is Incorrect**
**Option B:** Total Anomalous Pulmonary Venous Connection (TAPVC) typically presents with an enlarged cardiac silhouette and increased pulmonary vascular markings due to the abnormal connection of pulmonary veins to the systemic venous system.

**Option C:** Tricuspid atresia is characterized by an absent or abnormally developed tricuspid valve, leading to right-sided heart hypoplasia and a characteristic "egg-on-a-string" appearance on X-ray.

**Option D:** Ebstein's anomaly is a congenital defect of the tricuspid valve, characterized by an abnormal downward displacement of the valve into the right ventricle, resulting in right atrial enlargement and a characteristic "globular" cardiac silhouette on X-ray.

**Clinical Pearl / High-Yield Fact**
In TOF, the "boot-shaped" heart on X-ray is often accompanied by a decrease in the pulmonary vascular markings, indicating decreased pulmonary blood flow. This is a key radiological feature that can help differentiate TOF from other cyanotic heart defects.

**✓ Correct Answer: A. Tetralogy of Fallot**