Which artery carries oxygenated blood from the heart to the lower part of the leg?

The popliteal artery is the correct choice as it specifically carries oxygenated blood from the heart down to the lower part of the leg. This artery is a continuation of the femoral artery and is located behind the knee. It branches into the anterior and posterior tibial arteries, which further supply the lower leg and foot.

In contrast, the brachial artery supplies the arm, specifically the upper limb, with oxygenated blood and does not play a role in the blood supply to the legs. The internal jugular vein, while important for venous drainage, carries deoxygenated blood from the head and neck back to the heart, not oxygenated blood to the legs. The subclavian artery, although responsible for supplying blood to the upper limbs and parts of the chest, has no direct involvement with blood flow to the lower part of the leg.

Therefore, the popliteal artery is the artery specifically designated for this region, making it the correct answer.