Correct Answer: B

Rationale: The correct answer is B: eyes, nerves, and kidneys. In diabetes, major complications result from damage to small blood vessels that supply these organs. Damage to the eyes can lead to retinopathy, to the nerves causing neuropathy, and to the kidneys causing nephropathy. Choices A, C, and D are incorrect as they do not represent the typical major complications associated with diabetes.

Correct Answer: C

Rationale: The correct answer is C, Larynx. The larynx is part of the respiratory system, responsible for voice production and breathing. The alimentary canal is involved in the digestive process and includes structures like the oral cavity (mouth), pharynx, and esophagus. Choices A, B, and D are parts of the alimentary canal, where digestion occurs, making them incorrect answers.

Correct Answer: B

Rationale: Iron deficiency is the most common nutrient deficiency globally. It leads to anemia and affects many populations, especially women and children. Magnesium, selenium, and zinc deficiencies are important, but they are not as prevalent as iron deficiency on a global scale.

Correct Answer: C

Rationale: The correct answer is C: providing rigidity for the bones. Almost all of the calcium in the body is utilized for maintaining the strength and structure of bones and teeth. Calcium plays a crucial role in skeletal health by providing rigidity and support to the skeletal system. Choices A, B, and D are incorrect because while calcium is essential for various physiological functions like nerve transmission, cell energy production, and muscle contraction, the majority of calcium in the body is primarily allocated for bone health.

Correct Answer: B

Rationale: The correct answer is B: '21%'. Approximately 21% of persons in the United States who have HIV infection are unaware that they are infected. This percentage represents a significant portion of individuals who are not aware of their HIV status, highlighting the importance of increased testing and awareness campaigns. Choices A, C, and D are incorrect as they do not align with the estimated percentage provided in the context.