The predominant extracellular cation is

Correct Answer: B

Rationale: Sodium is the predominant cation in extracellular fluid, critical for osmotic balance and nerve function.

Correct Answer: C

Rationale: ADH, from the posterior pituitary, increases water reabsorption, concentrating urine.

Correct Answer: D

Rationale: Excess ADH causes water retention, diluting plasma sodium and leading to hyponatremia.

Correct Answer: D

Rationale: Cell damage releases intracellular potassium into the extracellular fluid, causing hyperkalemia.

Correct Answer: D

Rationale: Calcium is essential for bone structure, muscle function, clotting, and cardiac action potentials.