Correct Answer: C

Rationale: The correct answer is C: increased aldosterone secretion. Aldosterone, a hormone produced by the adrenal glands, increases sodium reabsorption in the kidneys, leading to retention of sodium and water in the interstitial fluid. Increased aldosterone secretion enhances the reabsorption of sodium, thereby increasing its retention. Choice A is incorrect because decreased aldosterone secretion would lead to less sodium reabsorption and increased excretion. Choice B is incorrect because increased ADH secretion primarily affects water reabsorption rather than sodium. Choice D is incorrect because decreased ADH secretion would lead to increased water excretion but not necessarily affect sodium retention.

Correct Answer: C

Rationale: In dehydration, the body first draws fluid from the interstitial space to maintain blood volume, leading to a decrease in interstitial fluid volume. This is why choice C is correct. Choice A is incorrect because intracellular fluid is not the first to be affected. Choice B is also incorrect as plasma volume reduction typically occurs after interstitial fluid loss. Choice D is incorrect as dehydration impacts both interstitial and intracellular fluid volumes.

Correct Answer: B

Rationale: The correct answer is B. The largest volume of water in the body is found inside the cells, known as intracellular fluid. This fluid makes up the majority of the body's total water content. Choices A, C, and D are incorrect because while plasma, interstitial fluid, and lymph are important components of the body's fluid compartments, they do not contain the largest volume of water in the body.

Correct Answer: B

Rationale: The correct answer is 'Intracellular fluid.' Intracellular fluid refers to the fluid contained within the cells, constituting a significant portion of the body's total water content. Choices A, C, and D are incorrect. Plasma is the liquid component of blood outside the cells, interstitial fluid is the fluid surrounding cells in tissues, and the combination of plasma and intracellular fluid is not the specific term for the fluid inside the cell.

Correct Answer: A

Rationale: The correct statement is that people with less body fat have more body water. This is because fat tissue contains less water compared to lean tissue, so individuals with less body fat generally have a higher percentage of body water. Choice B is incorrect as infants actually have more water per pound than adults due to their higher body water content. Choice C is incorrect as males typically have more body water per pound than females. Choice D is incorrect as infants have a higher water content per pound compared to adults.