**Core Concept**
Transposition of the great vessels (TGV) is a congenital heart defect where the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. This results in the aorta and pulmonary artery being in the wrong positions, leading to inadequate mixing of oxygenated and deoxygenated blood.

**Why the Correct Answer is Right**
In TGV, the normal sequence of blood flow is disrupted, resulting in the aorta carrying deoxygenated blood from the right ventricle and the pulmonary artery carrying oxygenated blood from the left ventricle. This leads to cyanosis, as the body's tissues receive inadequate amounts of oxygenated blood. The presence of congestive heart failure and cardiomegaly is due to the increased workload on the heart, which is trying to compensate for the abnormal blood flow. The normal first heart sound is consistent with TGV, as the mitral and tricuspid valves are functioning normally.

**Why Each Wrong Option is Incorrect**
**Option A:** Tetralogy of Fallot's is characterized by a combination of four anomalies: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. This condition typically presents with cyanosis, but the first heart sound is often abnormal due to the presence of a ventricular septal defect.

**Option B:** Ebstein anomaly is a congenital heart defect where the tricuspid valve is abnormally formed and the right ventricle is small. This condition often presents with cyanosis, but the first heart sound is typically abnormal due to the abnormal tricuspid valve.

**Option D:** Tricuspid atresia is a congenital heart defect where the tricuspid valve is absent or abnormally developed, preventing blood from flowing from the right atrium to the right ventricle. This condition often presents with cyanosis, but the first heart sound is typically abnormal due to the absence of the tricuspid valve.

**Clinical Pearl / High-Yield Fact**
In TGV, the cyanosis is often more pronounced in the first few hours of life, as the body's tissues are more sensitive to the lack of oxygen. This is known as "early cyanosis" and is a characteristic feature of TGV.

**✓ Correct Answer: C. Transposition of great vessels. Transposition of the great vessels**