Identifying the Radius Bone in the Arm

Steps:

• Recall the forearm consists of two main bones: the radius (lateral, thumb side) and ulna (medial, pinky side).
• Examine the diagram for the bone positioned on the thumb side of the forearm.
• Compare labels to anatomical positions: radius runs parallel to the ulna but allows forearm rotation.
• Match label C to the lateral forearm bone.

Why C is correct:

• The radius is defined as the lateral bone of the forearm, articulating with the humerus at the elbow and the thumb-side wrist bones.

Why the others are wrong:

• A labels the humerus, the upper arm bone proximal to the elbow.
• B labels the ulna, the medial forearm bone on the pinky side.
• D labels a wrist or hand bone, distal to the forearm.

Final answer: C