Which Feature Does Not Characterize the Malpighian Tubules of Insects

Which feature does not characterize the Malpighian tubules of insects?

A) They allow insects to excrete nitrogenous wastes with very little loss of water.
B) They rely on pressure differences to filter extracellular fluid into them.
C) Active transport brings solutes into them.
D) Water moves into tubules due to the high concentration of solutes within tubules.
E) Water helps flush tubule contents toward the gut.