**Core Concept**
Coarctation of the aorta is a congenital condition characterized by narrowing of the aortic isthmus, typically presenting with **hypertension** in the arms, **weak or delayed pulse** in the lower extremities, and might be associated with cardiac abnormalities. The condition can lead to increased pressure and flow in the intercostal arteries, which are branches of the aorta that supply the ribs. This increased flow can cause erosion of the lower borders of the ribs, leading to visible changes on radiographs.

**Why the Correct Answer is Right**
The correct answer choice is related to the fact that coarctation of the aorta leads to increased blood flow through the intercostal arteries, which in turn causes dilation of these arteries. This dilation results in erosion of the adjacent rib cortex, particularly on the lower border of the ribs, due to the increased blood flow and pressure. The changes are typically seen in the **3rd to 9th ribs**, as these are the ribs that have intercostal arteries supplying them, which are directly affected by the coarctation.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not accurately reflect the range of ribs typically affected by coarctation of the aorta.
**Option B:** Incorrect as it suggests an incorrect starting point for the rib changes associated with coarctation.
**Option C:** Incorrect because the range of ribs it suggests does not align with the pathophysiology of coarctation of the aorta.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the rib notching seen in coarctation of the aorta is usually more pronounced under the **3rd to 9th ribs**, as these are the primary locations where the intercostal arteries, which are affected by the coarctation, interface with the rib cage.

**Correct Answer:** D. 3rd to 9th ribs.