**Core Concept**
Coarctation of the aorta is a congenital or acquired narrowing of the aortic isthmus, typically presenting with hypertension, reduced or delayed femoral pulses, and rib notching on chest radiographs. The narrowed segment may be due to an intrinsic defect in the aortic wall or an extrinsic compression by an anomalous branch vessel.

**Why the Correct Answer is Right**
In coarctation of the aorta, the narrowed segment causes increased resistance to blood flow, leading to hypertension and a pressure gradient between the upper and lower body. This results in collateral circulation development, which can cause rib notching on chest radiographs due to erosion by dilated intercostal arteries. The classic radiographic sign of coarctation is the "figure-of-three" sign, where the aortic knob and the narrowed segment are separated by a "notch" formed by the dilated intercostal arteries.

**Why Each Wrong Option is Incorrect**
**Option A:** Left ventricular hypertrophy (LVH) is a common consequence of hypertension but is not a specific radiographic sign of coarctation of the aorta. LVH can be seen in various conditions, including essential hypertension, and is not pathognomonic for coarctation.
**Option B:** Pulmonary artery hypertension is not directly related to coarctation of the aorta, which primarily affects the aortic isthmus. While both conditions can be associated with hypertension, they have different radiographic and clinical presentations.
**Option D:** Cor pulmonale is a condition of right ventricular hypertrophy and failure due to pulmonary disease, which is not directly related to coarctation of the aorta.

**Clinical Pearl / High-Yield Fact**
Rib notching on chest radiographs is a classic sign of coarctation of the aorta, resulting from erosion by dilated intercostal arteries attempting to bypass the narrowed segment. This radiographic finding is often seen in conjunction with the "figure-of-three" sign, which consists of the aortic knob, the narrowed segment, and the dilated intercostal arteries.

**✓ Correct Answer: C. Coarctation of aorta**