Which 3D CAD function could be used to create a wire paper clip?

Creating a wire paper clip in 3D CAD typically requires a method that can define a curved, continuous shape. The function of using a spline is ideal for this task because a spline allows for the creation of smooth, freeform curves that can capture the complex geometry of a paper clip effectively.

A spline can be manipulated easily by placing control points that dictate the shape of the curve, allowing the designer to accurately depict the rounded portions and the bends associated with a paper clip. This flexibility makes it an excellent choice for modeling organic or non-linear forms.

Other functions are not as suitable due to their specific design characteristics. Extrusion primarily focuses on extending a shape along a straight path, which does not accommodate the complex curves needed for a paper clip's design. Revolution involves rotating a 2D profile around an axis, which is more suited for shapes that can be generated by circular symmetry, rather than the irregular, wire-like structure of a paper clip. Loft is used to create complex shapes between multiple profiles, which is unnecessary when your goal is to create a single continuous wire shape like that of a paper clip. Thus, the use of a spline stands out as the preferred method for this particular modeling task.