Which operation is used to combine two or more solid bodies into a single solid body?

The operation used to combine two or more solid bodies into a single solid body is referred to as "Unite." This function allows users to merge the volume of multiple solid bodies into one coherent entity, which is essential in design when complex shapes are created from simpler geometries.

In Siemens NX, the Unite operation effectively adds the volumes together, removing any overlapping or intersecting geometry to produce a smooth, singular body. This operation is commonly used in modeling when designers need to create more complex designs while maintaining the integrity of the overall structure.

The other options may imply similar actions but are not specifically defined for this exact function in Siemens NX. For instance, while "Merge" and "Weld" might suggest a joining of parts, they may not accomplish the same seamless integration as the Unite operation. "Connect" typically refers to linking features or surfaces rather than combining solid bodies into a unified volume. Hence, "Unite" stands out as the precise terminology used in this context.