Wettability is a property that describes how well a liquid spreads over or adheres to a solid surface. It is determined by the angle of contact formed between the liquid and the surface. The angle of contact is the angle at which the liquid-air interface meets the solid surface.

The correct answer to this question is option 'C', which states that the angle of contact between the surface and the liquid is the primary factor that determines the wettability of a surface.

Explanation:
The angle of contact is defined as the angle formed between the tangent to the liquid-air interface and the tangent to the solid-liquid interface at the point where they meet. It can be classified into three categories:

1. Wetting: When the angle of contact is less than 90 degrees, the liquid is said to wet the surface. In this case, the liquid spreads over the surface, forming a thin film. This indicates a high wettability.

2. Non-wetting: When the angle of contact is greater than 90 degrees, the liquid is said to be non-wetting. In this case, the liquid forms droplets on the surface, indicating a low wettability.

3. Partial wetting: When the angle of contact is exactly 90 degrees, the liquid is said to partially wet the surface. In this case, the liquid neither spreads nor forms droplets, but rather forms a meniscus.

The angle of contact is influenced by several factors, including surface tension, density, viscosity, and surface roughness. However, the primary factor that determines the angle of contact, and thus the wettability of a surface, is the surface tension of the liquid and the interfacial tension between the liquid and the solid.

Surface tension is the force that holds the molecules of a liquid together and is responsible for its tendency to minimize its surface area. It is influenced by the cohesive forces between the liquid molecules. A liquid with high surface tension will tend to form droplets on a surface, resulting in non-wetting behavior.

On the other hand, the interfacial tension between the liquid and the solid is determined by the adhesive forces between the liquid and the solid molecules. If the adhesive forces are stronger than the cohesive forces, the liquid will wet the surface and spread over it.

Therefore, the angle of contact, and consequently the wettability of a surface, is primarily determined by the balance between the cohesive and adhesive forces, which are influenced by surface tension. Thus, the correct answer is option 'C' - the angle of contact between the surface and the liquid.