Which of the following hormones is produced by the endocrine gland marked in the diagram?

Correct Answer: C

Rationale: Pineal gland (contextual) produces melatonin for sleep, not testosterone (gonads), glucagon (pancreas), thymopoietin (thymus), or vasopressin (pituitary). This distinguishes melatonin's role, key to circadian rhythms, contrasting with reproductive or immune hormones.

Correct Answer: A

Rationale: Glucagon targets liver hepatocytes for glycogenolysis, not pancreas (secretion site) or muscle (lacking receptors). 'A' inferred. This distinguishes glucagon's hepatic role, vital for glucose release, contrasting with insulin's broader targets.

Correct Answer: D

Rationale: Steroid hormones (e.g., cortisol) are lipid-soluble, taken orally as they resist digestion and absorb well water-insoluble trait aids stability. Carbohydrates aren't hormones energy sources. Peptides (e.g., insulin) and proteins degrade in the gut, requiring injection. Steroids' lipid nature distinguishes them, critical for oral administration, unlike digestible or non-hormonal options.

Correct Answer: B

Rationale: ADH (vasopressin) targets kidneys (water reabsorption via aquaporins) and blood vessels (vasoconstriction) raises blood pressure/volume. Adrenal cortex (aldosterone) and liver (metabolism) aren't ADH targets different systems. Liver-kidney omits vessels. Pituitary releases ADH, thyroid is unrelated. Kidney-vessel dual action distinguishes ADH, critical for fluid balance, unlike endocrine or metabolic pairs.

Correct Answer: D

Rationale: ACTH from anterior pituitary stimulates adrenal cortex to release cortisol/glucocorticoids stress response. Anterior pituitary makes ACTH, not target. Adrenal medulla (epinephrine) is neural. Kidneys respond to aldosterone, not ACTH directly. Adrenal cortex's ACTH-driven output distinguishes it, key to HPA axis, unlike source, neural, or renal options.