**Adhesion**

Adhesion is the attractive force between molecules of a liquid and the solid boundary surface with which it is in contact. It is the phenomenon responsible for the sticking together of different substances. The adhesion between a liquid and a solid surface is influenced by various factors, including the nature of the liquid and the solid, the surface roughness, and the temperature.

**Surface Tension**

Surface tension is the cohesive force between the molecules of a liquid that tends to minimize the surface area. It is responsible for the formation of droplets and the capillary rise of liquids in narrow tubes. Surface tension is not specifically related to the attraction between a liquid and a solid surface. It is more related to the cohesive forces within the liquid itself.

**Viscosity**

Viscosity is a measure of a liquid's resistance to flow. It is caused by the internal friction between the molecules of the liquid. Viscosity is not directly related to the attraction between a liquid and a solid surface.

**Capillary Action**

Capillary action is the ability of a liquid to flow in narrow spaces against the force of gravity. It occurs due to the combination of adhesive forces between the liquid and the solid surface and cohesive forces within the liquid itself. Capillary action is not the specific term used to describe the attraction between a liquid and a solid surface.

**Conclusion**

In conclusion, the correct answer to the given question is option A, adhesion. Adhesion refers to the attraction between molecules of a liquid and the solid boundary surface in contact with the liquid. It is responsible for the sticking together of different substances and plays a crucial role in various phenomena, such as wetting, spreading, and adhesion of coatings.