**Core Concept**
Coarctation of the aorta is a congenital cardiovascular anomaly characterized by an abnormal narrowing of the aorta, typically located at the junction of the aortic arch and descending aorta. This narrowing leads to increased resistance and pressure proximal to the lesion, while decreased pressure is observed distally. The resulting hemodynamic changes have significant clinical implications.

**Why the Correct Answer is Right**
The correct answer, **A. Lower limb pulses are barely palpable or absent**, is due to the reduced blood flow to the lower extremities caused by the coarctation. The narrowing of the aorta creates a significant obstruction to the flow of blood, leading to a decrease in the pulse pressure and pulse volume in the lower limbs. This results in diminished or absent lower limb pulses, which is a classic clinical finding in patients with coarctation of the aorta.

**Why Each Wrong Option is Incorrect**
**Option B:** This statement is incorrect because blood pressure is typically elevated proximal to the lesion (in the upper limbs) due to the increased resistance and pressure, while it is reduced distal to the lesion (in the lower limbs).

**Option C:** This statement is incorrect as coarctation of the aorta is more common in males than females, with a male-to-female ratio ranging from 3:1 to 5:1.

**Option D:** This statement is incorrect as hypertrophy of the lower ribs is not a characteristic finding in coarctation of the aorta.

**Clinical Pearl / High-Yield Fact**
In patients with coarctation of the aorta, the "collar-stud" sign may be observed on chest radiographs, where the aortic knob appears as a narrow collar surrounding a smaller descending aorta. This sign is a classic radiographic feature of coarctation.

✓ Correct Answer: A. Lower limb pulses are barely palpable or absent