**Core Concept**
Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four classic anomalies: ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy (RVH), and an overriding aorta. TOF is a cyanotic congenital heart disease, meaning it is associated with a bluish discoloration of the skin due to inadequate oxygenation of the blood.

**Why the Correct Answer is Right**
The correct answer, ASD (Atrial Septal Defect), is not typically associated with Tetralogy of Fallot. TOF is a complex cyanotic heart defect that involves a combination of VSD, pulmonary stenosis, RVH, and an overriding aorta. In contrast, ASD is a type of acyanotic congenital heart defect that involves a hole in the atrial septum, allowing blood to flow between the left and right atria. The presence of ASD would not be a characteristic feature of TOF.

**Why Each Wrong Option is Incorrect**
**Option A:** Cyanotic heart disease is actually true for TOF, as it is characterized by cyanosis due to inadequate oxygenation of the blood.
**Option B:** Right ventricular hypertrophy (RVH) is indeed a characteristic feature of TOF, as the right ventricle works harder to pump blood through the narrowed pulmonary valve.
**Option D:** Ventricular septal defect (VSD) is also a characteristic feature of TOF, as it allows blood to flow between the left and right ventricles.

**Clinical Pearl / High-Yield Fact**
TOF is a classic example of a cyanotic congenital heart defect that can be diagnosed prenatally using fetal echocardiography. It is essential to recognize the characteristic findings of TOF, including VSD, pulmonary stenosis, RVH, and an overriding aorta, to make an accurate diagnosis.

**✓ Correct Answer: C. ASD**