**Core Concept**
Peripheral aneurysms are abnormal dilations of arteries outside the aorta, typically involving the medium and small-sized arteries. The pathophysiology involves weakening of the arterial wall, often due to atherosclerosis, trauma, or infection.

**Why the Correct Answer is Right**
The most common peripheral artery affected by aneurysms is the popliteal artery. This is due to the unique hemodynamic forces and structural characteristics of this artery, which are prone to aneurysm formation. The popliteal artery is a medium-sized artery with a relatively high wall stress, making it susceptible to aneurysm development.

**Why Each Wrong Option is Incorrect**
**Option A:** The femoral artery is also a common site for peripheral aneurysms, but it is less frequently involved than the popliteal artery. The femoral artery is more commonly affected by aneurysms due to trauma or infection.
**Option B:** The superficial femoral artery is a part of the femoral artery and is not the most common site for peripheral aneurysms. While it can be involved, it is less frequently affected than the popliteal artery.
**Option C:** The iliac arteries are more commonly affected by aneurysms, but they are not peripheral arteries in the classical sense. They are often classified as aortic aneurysms due to their proximity to the aorta.
**Option D:** The radial artery is a small artery and is not typically involved in peripheral aneurysms. While it can be affected by aneurysms, it is less frequently involved than the popliteal artery.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a peripheral aneurysm, it is essential to consider the patient's medical history, including any history of trauma, infection, or atherosclerosis, as these factors can contribute to aneurysm formation.

**Correct Answer:** C. Popliteal artery