Which tool is used to create new bodies based on a selected face?

The tool used to create new bodies based on a selected face is the Loft Body. This tool allows for the creation of a solid body by defining two or more profiles and guiding the surface between them. When a face is selected as a starting point, this tool can generate a new body by extending or altering shapes in a controlled way, based on the geometry of the face you have chosen.

In contrast, the other tools serve different purposes. The Join Body tool is used to combine multiple bodies into a single body rather than creating a new one. The Split Body tool is for dividing a solid body into multiple parts without creating new bodies based on faces. The Extrude Body tool generates a solid based on a 2D sketch or outline, extending it in a specified direction, but does not specifically create new bodies from existing faces. Thus, Loft Body is the most suitable option for this particular operation in the context given.