Final answer:
All three scalene muscles can refer pain to all regions of the shoulder girdle, including the anterior, posterior, and superior regions, which corresponds to option D. All of the above.
Step-by-step explanation:
The scalenus muscles can refer pain to all regions of the shoulder girdle, so the correct answer is D. All of the above: anterior girdle, posterior girdle, and superior girdle. The pectoral girdle includes the clavicle and scapula and provides attachment points for muscles that support and move the upper limb.
While the question directly asks about the scalene muscles, which are not primarily movers or stabilizers of the pectoral girdle but accessory muscles for breathing, it is understood that referred pain from these muscles can be felt in the shoulder regions. This can occur due to complex musculoskeletal and nervous system interactions.