Around the thymus.
Around the liver, spleen, and upper gastrointestinal tract.
Behind the knee.
The colon and rectum.
The popliteal artery is a continuation of the femoral artery that runs through the back of the leg and the knee.
It is located in the popliteal fossa, a hollow space behind the knee. The popliteal pulse can be felt behind the knee.
Choice A is wrong because the thymus is a gland in the chest, not in the leg.
Choice B is wrong because the liver, spleen, and upper gastrointestinal tract are organs in the abdomen, not in the leg.
Choice D is wrong because the colon and rectum are parts of the large intestine, not the leg.