Final answer:
The 4D dimension in the context of space-time is typically considered to be 'time.' Time allows us to describe the position and change of objects as they occur over time, which adds a fourth aspect to the three spatial dimensions.
Step-by-step explanation:
The 4D dimension is often associated with the concept of time. In physics, when we refer to dimensions in the context of space-time, the three spatial dimensions are length, width, and height (or depth). The fourth dimension is typically time, which allows us to describe the position and changes of objects as they vary over time. Volume, which is derived from three-dimensional space and entails length cubed (L³), is an aspect of physical objects but not a dimension in the same context as time in the 4-dimensional space-time continuum.
Therefore, the correct answer to which one is usually considered the 4D dimension is c) Time.