**Core Concept**
The Snowman's heart sign on chest X-ray is a radiological finding associated with a specific congenital heart defect. This sign is characterized by a combination of enlarged cardiac silhouette, prominent pulmonary vascular markings, and an abnormal cardiac contour.

**Why the Correct Answer is Right**
Total anomalous pulmonary venous connection (TAPVC) is a congenital heart defect where the pulmonary veins do not connect normally to the left atrium. Instead, they connect to the right atrium or its tributaries, resulting in a characteristic "snowman" appearance on chest X-ray. This sign is due to the enlarged cardiac silhouette and the prominent pulmonary vascular markings, which give the heart a "snowman-like" appearance. The abnormal connection of the pulmonary veins leads to increased pulmonary blood flow and congestion, causing the characteristic radiographic findings.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ebstein anomaly is a congenital heart defect characterized by an abnormal tricuspid valve and right ventricular hypoplasia. While it can cause cardiac enlargement and right heart failure, it does not typically result in the Snowman's heart sign.
* **Option C:** Tetralogy of Fallot is a cyanotic congenital heart defect characterized by four components, including ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. The radiographic findings in Tetralogy of Fallot typically include a "boot-shaped" heart and decreased pulmonary vascular markings, not the Snowman's heart sign.
* **Option D:** Transposition of the great vessels is a congenital heart defect where the aorta and pulmonary artery are reversed. While it can cause cardiac enlargement and increased pulmonary blood flow, it does not typically result in the characteristic Snowman's heart sign.

**Clinical Pearl / High-Yield Fact**
The Snowman's heart sign is a classic radiographic finding in TAPVC, but it can also be seen in other conditions with increased pulmonary blood flow, such as left-sided heart failure or severe pulmonary embolism.

**✓ Correct Answer: B. Total anomalous pulmonary venous connection (TAPVC)**