Which line represents the starting and stopping points of a dimension?

The correct choice is dimension line. In technical drawings and engineering design, dimension lines are specifically used to indicate the extent of a dimension, serving as markers for the starting and stopping points of the measurement being conveyed. They run parallel to the dimension being measured and are typically capped with arrowheads at both ends, which point to the points being measured. This clear visual distinction allows anyone reading the drawing to quickly identify the exact locations between which the dimension applies.

Unlike extension lines, which extend from the features of the object being measured and do not show the specific dimension itself, dimension lines clearly communicate the measurement. Object lines depict the visible edges of an object, while hidden lines represent features that are not visible in the current view, neither of which indicate dimension or measurement extents. Thus, dimension lines are essential for any detailed technical drawing, making it easy to understand the sizes and distances involved in the design.