**Core Concept**
Tetralogy of Fallot, interrupted aortic arch, and tricuspid atresia are examples of ductus-dependent congenital heart diseases. These conditions require the patency of the ductus arteriosus for survival, as they involve obstructed blood flow to the systemic or pulmonary circulation. However, truncus arteriosus is a different entity, where a single common arterial trunk arises from the ventricles, bypassing the need for ductal patency.

**Why the Correct Answer is Right**
Truncus arteriosus is characterized by the absence of a normal separation between the aorta and pulmonary artery, resulting in a single artery that supplies both the systemic and pulmonary circulations. This unique anatomy allows for blood flow to both circuits without the need for ductal patency. In contrast, the other conditions listed rely on the ductus arteriosus to provide blood flow to the pulmonary or systemic circulation. The ductus arteriosus is a vital shunt in fetal life, connecting the pulmonary artery to the aorta, allowing blood to bypass the lungs.

**Why Each Wrong Option is Incorrect**
**Option A:** Tetralogy of Fallot involves a combination of four abnormalities: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. The ductus arteriosus is critical for maintaining blood flow to the lungs in this condition.
**Option B:** Interrupted aortic arch involves a complete or partial absence of the aortic arch, requiring the ductus arteriosus to maintain blood flow to the lower body. This condition is incompatible with life without ductal patency.
**Option C:** Tricuspid atresia involves the absence of the tricuspid valve, resulting in an obstructed right ventricular outflow. The ductus arteriosus is essential for maintaining blood flow to the pulmonary circulation in this condition.

**Clinical Pearl / High-Yield Fact**
In ductus-dependent congenital heart diseases, the ductus arteriosus is a vital shunt that maintains blood flow to either the systemic or pulmonary circulation. Failure to maintain ductal patency can lead to severe hypoxia and death.

**✓ Correct Answer: D. Truncus arteriosus**