4. Which of the following is the longest bone in the body? a. Humerus b. Tibia c. Sternum d. Femur

The longest bone in the human body is the **Femur**. Here's a brief explanation of each option: - **Humerus**: This is the bone of the upper arm, extending from the shoulder to the elbow. It is not the longest bone. - **Tibia**: This is the larger bone in the lower leg, also known as the shinbone, but it is shorter than the femur. - **Sternum**: This is the breastbone located in the center of the chest. It is flat and not a long bone. - **Femur**: This is the thigh bone and is the longest bone in the body, extending from the hip to the knee. Therefore, the correct answer is **d. Femur**.