Answer:
The correct answer is b. the urine volume decreased.
Step-by-step explanation:
As the solute gradient increases in the interstitial space the concentration of of solute increases in the fluid which draws out water present in the nephron tubules by osmosis in the interstitial fluid which is then reabsorbed by the body. So as the water comes out from filtrate the urine volume will decrease.
This process is helpful in reabsorbing the water and making the urine concentrated. Water reabsorption is necessary to maintain the volume of the blood present in the body. So increased solute gradient in interstitial space helps to convert isotonic filtrate to hypertonic urine.