Final answer:
The femoral artery and vein become the popliteal artery and vein as they pass behind the knee near the popliteal fossa, which corresponds to b) At the Knee Joint.
Step-by-step explanation:
The femoral artery and vein become the popliteal artery and vein when they pass posterior to the knee near the popliteal fossa. Specifically, this transition occurs as the femoral artery, which is a continuation of the external iliac artery after it passes through the body cavity, moves behind the knee and gives rise to the genicular artery. The corresponding femoral vein, which drains the upper leg and receives blood from several other veins in the region, similarly continues as the popliteal vein at this location. Therefore, the answer is b) At the Knee Joint.