**Core Concept**
Tetralogy of Fallot is a congenital cardiac anomaly characterized by four classic components: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. This condition leads to cyanosis due to reduced blood flow to the lungs and subsequent mixing of oxygenated and deoxygenated blood.

**Why the Correct Answer is Right**
Tetralogy of Fallot is the most common cyanotic congenital heart defect, accounting for approximately 5-7% of all congenital heart diseases. The combination of a ventricular septal defect and pulmonary stenosis results in a significant reduction in pulmonary blood flow, causing deoxygenated blood to be shunted directly to the systemic circulation, leading to cyanosis. This condition is often identified in infancy due to the presence of cyanosis, failure to thrive, and clubbing.

**Why Each Wrong Option is Incorrect**
**Option B:** Total Anomalous Pulmonary Venous Connection (TAPVC) is a cyanotic congenital heart defect where the pulmonary veins do not connect normally to the left atrium. While it is a serious condition, it is less common than Tetralogy of Fallot.

**Option C:** Transposition of the great vessels is a cyanotic congenital heart defect where the aorta and pulmonary artery are reversed. This condition requires immediate surgical intervention to correct, but it is less common than Tetralogy of Fallot.

**Option D:** Ebstein's anomaly is a congenital heart defect characterized by an abnormal tricuspid valve and right ventricular hypoplasia. While it can cause cyanosis, it is less common than Tetralogy of Fallot and typically presents with other symptoms such as atrial septal defects.

**Clinical Pearl / High-Yield Fact**
Tetralogy of Fallot is often associated with a "boot-shaped" heart on chest X-ray due to the right ventricular hypertrophy.

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