Which of the following structures is typically considered a retroperitoneal organ?

A. Urea: Urea is the major nitrogenous waste normally present in urine.
B. Albumin:Albumin in urine (albuminuria/proteinuria) is abnormal and suggests glomerular damage or increased filtration of plasma proteins.
C. Sodium: Sodium is a normal urinary electrolyte whose excretion varies with intake and hormonal control.
D. Creatinine:Creatinine is a normal waste product excreted in urine and used clinically to assess renal function.

A. It coordinates sensory perception and integration:That is the primary role of the nervous system (sensory integration, not reproduction).
B. It synthesizes hormones for energy metabolism:Endocrine organs (e.g., thyroid, pancreas) are chiefly responsible for metabolic hormone synthesis; while reproductive organs produce sex hormones, their primary system role is reproduction.
C. It ensures the continuation of the species: The main biological function of the reproductive system is to produce gametes and enable fertilization and development, ensuring species propagation.
D. It regulates fluid balance within the body: Fluid/electrolyte balance is primarily regulated by the renal and endocrine systems (kidneys, ADH, aldosterone).