Correct Answer: A

Rationale: Enlargement of the thyroid, known as a goiter, can compress the nearby structures in the neck, including the esophagus. This compression can lead to symptoms such as difficulty swallowing (dysphagia) or a sensation of pressure in the throat. Therefore, an enlarged thyroid gland is expected to affect swallowing. Choices B, C, and D are incorrect because a goiter primarily affects structures in the neck due to its physical enlargement, rather than directly impacting insulin levels, sleep, or digestion.

Correct Answer: D

Rationale: The correct answer is D. The skull is superior to the spinal cord, meaning it is located above the spinal cord in anatomical position. Superior in anatomy refers to a structure being positioned higher or above another structure in the body. Choices A, B, and C are incorrect because they refer to different directional relationships. Anterior means in front of, posterior means behind, and lateral means to the side. In this case, the relationship between the skull and the spinal cord is based on a superior-inferior orientation.

Correct Answer: D

Rationale: The correct answer is D, the radius. The axial skeleton comprises bones located along the central axis of the body. It includes the skull, ribs, breastbone (sternum), vertebrae, and sacrum. The radius, on the other hand, is a bone of the forearm, part of the appendicular skeleton. The appendicular skeleton consists of the bones of the limbs and their girdles, not the central axial bones.

Correct Answer: B

Rationale: The urethra belongs to both the urinary and reproductive systems. In the urinary system, it functions as a passage for urine from the bladder to exit the body. In the reproductive system, it serves as a conduit for the expulsion of semen during ejaculation. Choice A is incorrect because the urethra is not part of the endocrine system. Choice C is also incorrect because the urethra is not primarily associated with the endocrine system. Choice D is incorrect as the urethra is not part of the digestive or cardiovascular systems.

Correct Answer: C

Rationale: The alveoli are the primary site for gas exchange in the respiratory system. These tiny air sacs in the lungs are where oxygen is taken up into the bloodstream and carbon dioxide is released from the bloodstream into the lungs to be exhaled. The trachea (Choice A) is the windpipe that carries air to and from the lungs but is not directly involved in gas exchange. Bronchioles (Choice B) are smaller airway branches that lead to the alveoli but do not participate in gas exchange themselves. The larynx (Choice D) plays a role in producing sound and protecting the airway but is not primarily responsible for gas exchange.