What are the main bones that comprise the lower extremities?

The lower extremities are primarily composed of four main bones: the femur, patella, tibia, and fibula. The femur, also known as the thigh bone, is the largest bone in the body and plays a crucial role in supporting the weight of the upper body during standing, walking, or running. The patella, commonly referred to as the kneecap, protects the knee joint and assists in the mechanics of knee extension. The tibia, known as the shinbone, is the larger of the two bones in the lower leg and bears most of the body's weight, while the fibula serves as a support structure alongside the tibia but does not bear significant weight itself.

In contrast, the options which include bones like the ulna, radius, clavicle, and vertebrae are not relevant to the lower extremities, as they are either part of the upper limb or the spinal column. Therefore, the selection that includes the femur, patella, tibia, and fibula accurately reflects the main bones that make up the lower extremity, emphasizing their functional importance in locomotion and stability.