The femur is the longest bone in the human body. It is located in the upper leg and connects the hip to the knee. The femur is a long, strong bone that supports the weight of the body and allows for movement of the leg. It is also the largest bone in the body.
The fibula is a long, thin bone located on the outside of the lower leg. It connects the knee to the ankle and helps to support the weight of the body. The fibula is not as strong as the femur and is not as important for movement.
The radius is a long, thin bone located on the thumb side of the forearm. It connects the elbow to the wrist and helps to support the weight of the hand. The radius is not as long as the ulna and is not as important for movement.
The stapes is the smallest bone in the human body. It is located in the middle ear and helps to transmit sound waves from the eardrum to the inner ear. The stapes is not a long bone and is not important for movement.
Therefore, the correct answer to the question “Which is the longest bone in the human body?” is D. Femur.