A liquid does not wet the sides of a solid, if the angle of contact is

The correct option is Obtuse (More than 90°).

Understanding Contact Angle:
When a liquid surface meets a solid surface, it forms a curve called a meniscus. The angle between the tangent to the liquid surface at the point of contact and the solid surface inside the liquid is defined as the angle of contact ($\theta$).

The behavior of the liquid (whether it wets the solid or not) depends on the relative strengths of two forces:
1. Cohesive forces: The attractive forces between the molecules of the same substance (liquid-liquid molecules).
2. Adhesive forces: The attractive forces between molecules of different substances (liquid-solid molecules).

Analysis of Different Cases:
- When adhesive forces are stronger than cohesive forces: The liquid molecules are pulled strongly toward the solid surface. As a result, the liquid rises along the solid boundary, forming a concave meniscus, and the liquid wets the solid surface. In this case, the angle of contact is acute ($\theta <90°$). Examples include water on glass.
- When cohesive forces are stronger than adhesive forces: The liquid molecules prefer to stay bound together rather than spreading on the solid. The liquid surface curves away from the solid wall, forming a convex meniscus, and the liquid does not wet the solid surface. In this case, the angle of contact is obtuse ($\theta >90°$). Examples include mercury on glass.

Therefore, a liquid does not wet the sides of a solid if the angle of contact is obtuse (more than 90°).