Final answer:
The lateral lower leg bone in anatomical position is the fibula, which is slender and positioned on the leg's lateral side.
Step-by-step explanation:
In anatomical position, the bone that is the lateral lower leg bone is the fibula. This bone is known to be slender and located on the lateral side of the leg. The fibula does not bear weight like the tibia, which is the larger bone situated medially and bears the weight of the body. The other bones listed such as the femur, which forms the thigh, and the patella, which is the kneecap, are located in different parts of the lower limb. Therefore, the correct answer is 3) Fibula.