Systemic disease often manifests in the oral cavity first. Disease within the oral cavity can cause systemic complications.

Correct Answer: A

Rationale: Both statements are true. Systemic diseases can often present with oral manifestations before other systemic signs appear. Additionally, oral diseases can have systemic implications by affecting a person's overall health, such as through inflammation or compromised nutrient intake. Choice B is incorrect because both statements are true, as supported by medical literature. Choice C is incorrect because the second statement is also true. Choice D is incorrect because the first statement is true.

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.

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: B

Rationale: The correct answer is B: Iron. The provided extract mentions that iodine deficiency can cause delayed tooth eruption, enlarged tongue, stillbirths, altered craniofacial growth, sensitivity to cold, dry skin, depression, and goiter. Zinc, Sodium, and Potassium are not associated with these specific symptoms. Zinc deficiency can lead to other health issues but not the ones mentioned. Sodium and Potassium imbalances do not typically result in the symptoms described in the question.

Correct Answer: D

Rationale: The correct answer is D: Potassium. Chronic potassium deficiency can lead to hypertension, heart attack, stroke, kidney stones, and osteoporosis. Patients experiencing this deficiency may feel tired, weak, and irritable without knowing the cause. Choice A (Zinc) is incorrect as zinc deficiency presents with different symptoms. Choice B (Iron) deficiency is associated with anemia symptoms, not the conditions listed. Choice C (Sodium) deficiency typically manifests as muscle cramps, weakness, and confusion, not the conditions described in the question.