It's Very Rare for Two Sets of Capillaries to Occur

Multiple Choice

It's very rare for two sets of capillaries to occur in sequence;what physiological challenge could occur in such a situation?

A) All the pressure that maintains blood flow would be depleted in the first capillary set.
B) Blood arriving at a capillary with a low oxygen concentration would pull oxygen from the cells rather than deliver it.
C) Signaling molecules (a hormone,for example) would be removed at the first capillary;the more distant cells could not be regulated.
D) The combined production of carbon dioxide from twice as many cells would irreparably damage the red blood cell.