**Core Concept**
The question is testing the knowledge of the most common type of congenital cyanotic heart disease, which refers to a group of heart defects present at birth that lead to cyanosis (a bluish discoloration of the skin and mucous membranes) due to impaired oxygenation of the blood. These defects involve abnormalities in the structure of the heart, including the septa, valves, and major blood vessels.

**Why the Correct Answer is Right**
Tetralogy of Fallot (TOF) is the most common type of cyanotic congenital heart disease, accounting for approximately 5-7% of all congenital heart defects. TOF is characterized by four key features: ventricular septal defect (VSD), pulmonary stenosis (narrowing of the pulmonary valve), right ventricular hypertrophy (enlargement of the right ventricle), and an overriding aorta (the aorta sits on top of the VSD). The combination of these features leads to reduced blood flow to the lungs and subsequent cyanosis. The pathophysiology of TOF involves the right-to-left shunting of blood through the VSD, bypassing the lungs and resulting in systemic desaturation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hypoplastic left heart syndrome is a cyanotic congenital heart disease, but it is relatively rare compared to TOF. It involves underdevelopment of the left side of the heart, leading to impaired oxygenation of the blood.
* **Option B:** Transposition of the great arteries is another cyanotic congenital heart disease, but it is less common than TOF. It involves a reversal of the positions of the aorta and pulmonary artery, leading to impaired oxygenation of the blood.
* **Option C:** Ebstein's anomaly is a rare cyanotic congenital heart disease characterized by abnormal development of the tricuspid valve and right ventricle. While it can lead to cyanosis, it is not the most common type of cyanotic congenital heart disease.

**Clinical Pearl / High-Yield Fact**
The "four Ts" of Tetralogy of Fallot are: **T**runcus arteriosus (overriding aorta), **T**ransposition of the great arteries (not a characteristic feature of TOF, but worth remembering), **T**ricuspid atresia (not a characteristic feature of TOF), and **T**etralogy of Fallot itself.

**Correct Answer:** C. Ebstein's anomaly is not the correct answer.