[Solved] ________ refers to engaging in sexual activity in exchange for money or goods. A)Erotica B)Deviance C)Prostitution D)Sexting Solute Gradient: A solute gradient involves the variation of solute concentration across a distance, which can drive various biological processes, including diffusion and osmosis. Medullary Concentration Gradient: A gradient of solute concentration in the kidney medulla that facilitates water reabsorption and urine concentration through osmosis. Urea Molecules: Organic compounds and the main nitrogen-containing substance in the urine of mammals, formed in the liver from ammonia and carbon dioxide. Ascending Limb: The part of the loop of Henle in the nephron that transports fluid from the lower to the upper parts of the kidney.