The forearm is made up of the radius and ulna bones. Hence the correct option is b.
The forearm, a crucial component of the human upper limb, is primarily composed of two long bones: the radius and the ulna. These bones run parallel to each other, connecting the elbow joint to the wrist joint. The ulna is located on the inner side of the forearm and is often referred to as the "medial bone," while the radius is positioned on the outer side or the "lateral bone."
Together, the radius and ulna contribute to the structural framework and functionality of the forearm, facilitating essential movements such as pronation and supination. While the scapula and humerus are indeed part of the upper limb, they are not direct components of the forearm; instead, they form the shoulder and upper arm regions. The metacarpal bones and phalanges are associated with the hand and fingers, further emphasizing the distinct anatomical components within the upper limb. Hence the correct option is b.