Vitamin deficiencies, especially the B-complex vitamins, seldom occur in isolation. Folate, a B-complex vitamin, is the exception because it functions separately from other vitamins.

Correct Answer: C

Rationale: The first statement is true; the second is false. If a deficiency of one vitamin is suspected, symptoms of other vitamin B deficiencies also may be present. Folate deficiencies usually occur with other nutrient deficiencies. Specifically, folate functions in conjunction with vitamins B12 and C in maintaining normal levels of mature red blood cells.

Correct Answer: C

Rationale: Vitamin A can be stored in the liver to meet basic needs for at least 1 year. This storage capacity allows the body to have a reserve of Vitamin A to sustain its needs over an extended period. Choices A, B, and D are incorrect because they underestimate the storage capacity of Vitamin A in the liver, which can last longer than these durations.

Correct Answer: C

Rationale: The correct answer is C: Secondary deficiency. A nutritional deficiency resulting from decreased intake is called a primary deficiency. On the other hand, a secondary deficiency refers to a vitamin deficiency caused by inadequate absorption or use, increased requirements, excretion, or destruction. Choice A, 'Unmeasurable,' is incorrect as it does not describe a type of nutritional deficiency. Choice B, 'Primary deficiency,' is incorrect as it refers to a deficiency caused by decreased intake, not inadequate absorption. Choice D, 'Codependent,' is incorrect as it is unrelated to the context of nutritional deficiencies.

Correct Answer: A

Rationale: Both the statement and the reason are correct and related. The Institute of Medicine (IOM) recommends 18 mg of iron per day for women 19 to 50 years old, 8 mg/day for women 51 years old and older, and men 19 years old and older. During menstruation, women lose blood containing iron, leading to a higher iron requirement in premenopausal women compared to men or postmenopausal women. This increased demand aims to replenish the iron lost during this physiological process. Therefore, the statement and reason are directly linked, explaining why the RDA for iron is higher in premenopausal women than in men or postmenopausal women. Choices B, C, and D are incorrect as they do not accurately assess the relationship between the statement and the reason provided in the question.

Correct Answer: B

Rationale: The correct answer is B. Magnesium plays an important role in maintaining calcium homeostasis and preventing skeletal abnormalities. It is involved in more than 300 enzymatic reactions, including energy metabolism, insulin activity, and glucose use. Magnesium is vital to the structural integrity of heart muscle and other muscles and nerves. While magnesium does play a role in blood clotting, nerve impulses, muscle contraction, relaxation, ATP energy release, and metabolism of fats, carbohydrates, proteins, the primary physiologic role of magnesium in the body is related to calcium homeostasis and maintaining the structural integrity of the heart muscle. Choice A is incorrect because it includes functions of magnesium, but they are not its primary physiologic role. Choice C is incorrect as magnesium has several known metabolic functions. Choice D is incorrect because although magnesium is involved in ATP energy release and metabolism, its primary role is related to calcium homeostasis and structural integrity of muscle.

Correct Answer: A

Rationale: Both the statement and the reason are correct and related. Inadequate intake of vitamin A in lower socioeconomic groups is due to a lack of resources to purchase and consume vegetables and fruits. This is supported by the fact that the average intake in the United States meets the Recommended Dietary Allowance (RDA) for vitamin A intake, except in lower socioeconomic groups. These individuals often lack the financial means to buy, prepare, and eat a variety of fruits and vegetables, leading to deficiencies. It's important to note that because vitamin A can be stored in the liver, most adults have sufficient quantities to maintain health. Choices B, C, and D are incorrect because the statement and reason are both accurate and logically connected, as the lack of resources directly impacts the ability to obtain necessary sources of vitamin A.

Correct Answer: B

Rationale: The correct answer is B. Water-soluble vitamins do not develop deficiencies rapidly because the body does not store them for long periods. They must be obtained through food constantly. Choice A is correct because water-soluble vitamins often act as coenzymes in various metabolic reactions. Choice C is correct as daily intake of water-soluble vitamins is necessary since they are not stored in the body. Choice D is incorrect as water-soluble vitamins are absorbed primarily in the small intestine, particularly in the duodenum and ileum, not the jejunum.

Correct Answer: C

Rationale: While UV radiation can penetrate uncovered skin and convert a precursor of vitamin D to vitamin D3, sunscreen does block the formation of vitamin D3. Sunscreen is recommended by dermatologists to prevent sunburn and reduce the risk of skin cancer. The other choices are correct: the body can produce sufficient vitamin D from sunlight, UV radiation can convert a precursor of vitamin D to vitamin D3, and skin generally produces less vitamin D as a person ages.

Correct Answer: A

Rationale: The principal cation in plasma and interstitial fluid is sodium. Sodium plays a crucial role in maintaining fluid balance and is the primary cation in extracellular fluids like plasma and interstitial fluid. Potassium is the primary cation within cells, not in extracellular fluids, making it an incorrect choice. Calcium and magnesium are essential minerals but are not the principal cations in plasma and interstitial fluid, so they are also incorrect choices.