Which of the Following Observations Provides the Strongest Evidence Against

Which of the following observations provides the strongest evidence against root pressure being the principal mechanism of water transport in the xylem?

A) Not all soils have high concentrations of ions.
B) Root pressure requires movement of water into the xylem from surrounding cells in the roots.
C) Over long distances, the force of root pressure is not enough to overcome the force of gravity.
D) There is no water potential gradient between roots and shoots.