Which chest wall structure is explicitly listed as visible on ultrasound in the source material?

• A. Rib
• B. Lymph nodes
• C. Cooper's ligaments
• D. Pectoralis muscle

Answer: (A)

The key idea is that bone structures on ultrasound provide a bright, highly echogenic cortex with a clean posterior shadow, which makes them easy to recognize as landmarks. In this material, the rib is explicitly listed as visible on ultrasound, so it serves as a clear chest wall landmark and helps distinguish the chest wall from the breast tissue underneath. While other structures like pectoralis muscle, Cooper’s ligaments, or regional lymph nodes can be seen in breast ultrasound, they aren’t the structure the source specifically calls out as visible on ultrasound in this context. The rib’s distinct cortical line and shadowing make it the most reliable and explicitly listed chest wall structure in the material.