Which of the following supports the finding that sugar translocation in phloem is an active energy- requiring) process?

A) Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced.
B) Sugar is translocated in a bi- directional manner.
C) Strong pH differences exist between the cytoplasm of the companion cell and the mesophyll cell.
D) Movement of water occurs from xylem to phloem and back again.
E) H⁺- ATPases are abundant in the plasma membranes of the mesophyll cells.