Concept: The organ shown is the kidney, whose main role is osmoregulation.
Explanation:The kidney filters blood, removes waste, and produces urine.
Its primary function is osmoregulation — controlling the balance of water and dissolved salts in the body.
Vasoconstriction refers to narrowing of blood vessels and is not the kidney’s chief function.
Heat production occurs mainly in muscles and the liver, not in the kidney.
Although the kidney secretes some hormones (e.g., erythropoietin), that is not its major role compared with osmoregulation.
Answer: B. osmoregulation
