In computer aided design (CAD), solid models can be constructed using:

The correct option is boundary representation (B-rep).

In Computer-Aided Design (CAD) and computer graphics, 3D modeling techniques are broadly classified into solid modeling, surface modeling, and wireframe modeling.

To understand why boundary representation (B-rep) is the correct answer, let's break down the concepts:
1. Solid Modeling: This involves representing the solid physical volume of a 3D object. A valid solid model must define what is inside and what is outside of the object, ensuring it is watertight and physically realizable. The two most common mathematical representations used for solid modeling are Constructive Solid Geometry (CSG) and Boundary Representation (B-rep).
2. Boundary Representation (B-rep): This method represents a solid by defining its boundary surface, which separates the points inside the solid from the points outside. The solid is described as a collection of connected topological elements (faces, edges, and vertices) combined with geometric definitions for those elements.
3. Bezier curves, B-splines, and NURBS (Non-Uniform Rational B-Splines): These are mathematical representations used primarily for defining curves and surfaces (wireframe and surface modeling). While B-rep models can use NURBS or Bezier patches to define the geometry of their individual curved faces, these curves/surfaces on their own do not represent a closed, volumetric solid object.

Therefore, boundary representation (B-rep) is the method used to construct solid models in CAD.