Which of the following is not a part of pectoral girdle?

Acetabulum is a cavity present in the coxal bone which is a part of the pelvic girdle.

Each half of the pectoral girdle consists of a scapula and a clavicle. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion. Below the acromion is a depression called the glenoid cavity.