Which of the following statements about H2O movement in the nephron is/are true?
a) H2O diffuses down its osmolarity gradient directly across the apical (luminal) and basolateral membranes directly through the lipid bi-layer.
b) The osmolarity gradient that drives H2O diffusion (osmosis) is created by the re-absorption of solutes along the nephron, particularly Na+.
c) H2O re-absorption is directly coupled to (directly follows) Na+ re-absorption in all segments of the renal tubule.
d) Water channels called aquaporins must exist in the apical and basolateral membranes for significant H2O re-absorption to occur.
e) H2O molecules use Na+/H2O co-transporters to move across the membrane.