Answer:
a. capillary action of liquid in plant stems
Explanation:
Vascular plants need to transport water from roots to stem and leaves. For this purpose, water molecules adhere to xylem cell walls (xylem is one of the two classes of transport tissues in higher plants). Adhesion, also known as capillary action, is a mechanism produced when water molecules cling to xylem cell walls. Thus, adhesion can be defined as a molecular mechanism caused by the attraction between molecules, in this case, between molecules of the xylem and water molecules.
