Which of the following statements about the ascent of water in tall trees is true? (Select all that apply.)
a. Plants must expend their own metabolic energy to power the ascent of water into treetops.
b. The evaporation of water from leaf surfaces pulls water from the roots to the canopy of a tall tree.
c. The ascent of water in the xylem is fastest when the stomata are closed.
d. The ultimate source of energy for the ascent of water is the sun.
e. All of the above are true.