Which of the following is not a role of the radius?

The radius, one of the two long bones in the forearm, plays several critical roles, including supporting arm movement and acting as an attachment point for muscles. It allows for a range of motions at the elbow and wrist, enabling effective function of the upper limb. It also serves as an anchor for various muscles that contribute to the movement of the arm and hand.

The radius does not have a role in directly isolating the femur, which is the thigh bone. The femur and radius are part of different limb structures; the femur is situated in the lower limb (the leg) while the radius is in the upper limb (the arm). Thus, the function of isolating the femur is not relevant to the radius, making that option the correct answer.

In contrast, the other roles—support for arm movement, attachment points for muscles, and protection of nerves—are accurately associated with the radius's functions in the body. The design and placement of the radius are closely linked to its supportive and muscular roles, while its anatomical location contributes to the protection of nearby structures, such as nerves in the arm.