Which element of design extends from a plane and is defined by its form?

The correct choice is volume because it is an element of design that extends from a plane into three dimensions, creating a physical body or mass that occupies space. Volume is defined by its shape and the boundaries that enclose that space, making it distinct from other elements like point, line, and shape.

While point represents a singular location in space and line is a series of points extending in one direction, shape is two-dimensional, defined only by its height and width. Volume, on the other hand, incorporates depth, allowing it to convey mass and occupy physical space in the design context. Understanding volume is crucial for architects and designers as it conveys the solidity and spatial relationships of objects within a given environment.