The correct option is D All of the above
The mechanism of the ascent of sap in plants occurs due to the activity of the living cells. The factors responsible are
root pressure- plant roots absorb the excess of water by an active process and builds up a hydrostatic pressure within the root system, called root pressure. This activity pushes the water upwards all along the length of the stem.
Transpiration -The pulling force that operates on xylem water columns is called Transpiration Pull or Suction Pressure.
Capillary action along with the root pressure, the ascent of sap is mainly due to passive forces that develop within the plant, due to certain environmental factors that act upon the plant. tracheids and vessels of the xylem behave as capillary tubes. Ascent of sap is partly due to the capillarity of these tissues. Thus, the correct answer is option D.