Glucagon secretion is stimulated by:

Correct Answer: D

Rationale: Exercise stimulates glucagon secretion to mobilize glucose. Somatostatin, glucose, and insulin inhibit it, while ketones have a lesser direct effect.

Correct Answer: A

Rationale: Chromium enhances insulin action; its deficiency leads to insulin resistance and glucose intolerance.

Correct Answer: B

Rationale: Colipase, secreted by the pancreas, activates pancreatic lipase by aiding fat digestion; cholera acts extracellularly, B_{12} uses intrinsic factor, and oxalates inhibit Ca2+ absorption.

Correct Answer: D

Rationale: ~9 L of fluid enters the gut daily: 2 L ingested, 7 L from secretions (saliva, gastric, pancreatic, etc.).

Correct Answer: D

Rationale: LH is produced by the anterior pituitary gland. It targets the ovaries. LH stimulates ovulation and production of progesterone. LH does not affect maintenance of secondary sex characteristics, fluid retention, or menstrual cycle regularity.