16. The substances that are reabsorbed did not diffuse (move) from the nephron bowl into the renal vein cup. You needed to use lots of energy to make reabsorption happen. Which
process do you think the kidney uses to transport these substances from the nephron to the
renal vein-active transport or diffusion (passive transport)? Explain your answer.

Active transport.

Explanation:

The kidney uses active transport  to move these substances from the nephron to the  renal vein because these substances did not moves from the nephron bowl to the renal vein through simple diffusion so for this purpose active transport is used in which energy is spent in order to move the substances from one region to another so we can say that kidney must use active transport to move reabsorbed substances from the nephron to the  renal vein.