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: 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.

Correct Answer: A

Rationale: Wernicke-Korsakoff syndrome is indeed associated with thiamine (vitamin B1) deficiency. This syndrome is commonly seen in individuals with chronic alcoholism due to poor diet and impaired thiamine absorption. Thiamine is essential for normal brain function and energy metabolism. Riboflavin (B2) deficiency can lead to symptoms like sore throat and swollen mucous membranes, not Wernicke-Korsakoff syndrome. Niacin (B3) deficiency causes pellagra, characterized by dermatitis, diarrhea, dementia, and death, but not Wernicke-Korsakoff syndrome. Pyridoxine (B6) deficiency can result in dermatitis, glossitis, and peripheral neuropathy, but it is not associated with Wernicke-Korsakoff syndrome.

Correct Answer: D

Rationale: The correct answer is D. Calcium within saliva does not increase dental caries; in fact, the buffering action provided by calcium and phosphate in saliva inhibits caries formation by preventing the dissolution of enamel by plaque biofilm. Choice A is correct as saliva is indeed supersaturated with calcium. Choice B is correct as saliva serves as a source of calcium to mineralize an immature or demineralized enamel surface. Choice C is correct as calcium and phosphate in saliva do provide a buffering action to protect teeth from acids.

Correct Answer: D

Rationale: The correct answer is D, Osmosis. Osmosis is the process where water moves from an area of low solute concentration to an area of high solute concentration. This movement equalizes the solute concentration in intracellular and extracellular fluids. Choices A, B, and C are incorrect because they do not describe the movement of water based on solute concentration levels.