Answer:
The correct answer is - ulnar radial notch and the annular ligament.
Explanation:
The head of the radius and the ring formed by the ulnar radial notch and the annuar ligament that helps in an essential action or movement of supination and pronation of the upper limbs.
These two markings form a pivot joint which is known as the proximal radioulnar joint. It allows a rotational movement of the radius on the ulna at the distal end.
