Final answer:
The clavicle is the only fixed support for the pectoral girdle that is part of the pectoral girdle itself, connecting directly to the axial skeleton at the sternoclavicular joint.
Step-by-step explanation:
The Only Fixed Support for the Pectoral Girdle
The question asks about the only fixed support that is part of the pectoral girdle and connects it to the axial skeleton. Of the options provided, the correct answer is B) clavicle. The pectoral girdle consists of two bones: the scapula and the clavicle. The scapula is located posteriorly, and the clavicle or collarbone is located anteriorly. The clavicle acts as a strut between the sternum and the shoulder blade. It is the clavicle that articulates with the sternum at the sternoclavicular joint, providing the sole fixed support for the pectoral girdle to the axial skeleton. The scapula, while part of the pectoral girdle, is not fixed; it is held in place by muscles and does not directly articulate with the ribs.
The clavicle is essential as it helps to transfer force from the upper limbs to the trunk and provides support and protection for underlying nerves and blood vessels. Therefore, for the student's question, the correct answer is B) clavicle, as it is the only bone that provides a direct and fixed support for the pectoral girdle to the axial skeleton through the sternoclavicular joint.