Final answer:
The correct spelling of the upper arm's long bone is 'B. Humerus'. It connects the shoulder and elbow and is essential to the arm's anatomy.
Step-by-step explanation:
The correct spelling of the long bone of the upper arm is B. Humerus. The humerus is the largest and longest bone of the upper limb and the only bone of the arm. It plays a critical role as it articulates with the scapula at the shoulder and with the forearm at the elbow.
The anatomy of the arm includes the humerus of the upper arm, the radius and ulna of the forearm, bones of the carpus (wrist), metacarpus (palm), and phalanges (digits).