Final answer:
Blood colloid osmotic pressure, a result of plasma proteins, tends to draw water out of the nephron's filtrate and into the plasma, thereby facilitating the reabsorption of water (option b).
Step-by-step explanation:
Blood colloid osmotic pressure (BCOP), driven by the concentration of plasma proteins, tends to draw water out of the filtrate and into the plasma. This osmotic pressure is crucial for the reabsorption of water across the semipermeable capillary membrane, as the proteins act as solutes that create an osmotic gradient. Water moves towards the higher osmotic pressure within the blood capillaries to balance the solute concentration.
In the kidney, this principle helps in the reabsorption of water from the nephron back into the blood vessels. Specifically, BCOP is responsible for pulling water back during the passive reabsorption processes occurring in the peritubular capillaries and vasa recta surrounding the nephron, which directly counteracts filtration at the glomerulus. It is not responsible for the transport processes in the loop of Henle or for the effects of ADH and aldosterone in the collecting duct.
Therefore, blood colloid osmotic pressure or high solute concentration in the plasma tends to draw water out of the filtrate and into the plasma, which corresponds to option b.