Which line type is used to denote the center of arcs and circles in drawings?

The center line is specifically designed to indicate the centers of arcs and circles in technical drawings. This line type is typically represented by alternating long and short dashes, making it easily distinguishable from other line types used in drafting. By using center lines, drafters can convey important information about symmetry, rotation, and axis alignment in various components. When a circle or an arc is present, indicating its center point is crucial for accurate measurements and construction, which is precisely what center lines achieve.

Other line types serve different purposes; hidden lines indicate features that are not visible in a particular view, break lines show where a view is broken or interrupted, and phantom lines represent alternate positions or paths of action. Each of these has its own distinct functions that are not suitable for denoting the centers of arcs and circles. Thus, the center line is the correct choice for this purpose.