**Boundaries of a Surface**

A surface is a two-dimensional object that can be defined as a set of points in three-dimensional space. In the context of geometry, the boundaries of a surface refer to the curves that enclose the surface and separate it from its surroundings. These boundaries can be classified into different types, including lines, curves, surfaces, and points. However, when considering the boundaries of a surface, the correct answer is option 'B', which refers to curves.

**Explanation**

1. **Lines**: Lines are one-dimensional objects that extend infinitely in both directions. They can be considered as the boundaries of a plane or a flat surface. However, when dealing with a three-dimensional surface, lines alone are not sufficient to enclose it as they lack the necessary curvature to form boundaries.

2. **Curves**: Curves, on the other hand, are two-dimensional objects that can have various shapes and curvatures. They can enclose and define the boundaries of a surface. Curves can be open or closed, and they can have different degrees of smoothness or roughness. Examples of curves include circles, ellipses, parabolas, and other irregular shapes.

3. **Surfaces**: Surfaces themselves cannot be considered as boundaries since they represent the entire two-dimensional object. Surfaces can have boundaries, but they are not boundaries themselves. A surface can be defined by its boundaries, which are formed by curves.

4. **Points**: Points are zero-dimensional objects and do not have any dimensions or boundaries. They are infinitesimally small and cannot be considered as boundaries of a surface.

Therefore, when considering the boundaries of a surface, the correct choice is option 'B' - Curves. Curves define the shape and enclose the surface, separating it from its surroundings. These curves can be smooth or irregular, closed or open, and they can vary in shape and size.