Which best describes objects that line up when folded along a crease?

The best description of objects that line up neatly when folded along a crease is congruent objects. Congruent objects are those that are identical in shape and size, so when you fold one over the other along a defined line, such as a crease, all corresponding points and dimensions match up precisely. This property makes it easy to see that the two objects align perfectly with no discrepancies.

In contrast, similar objects refer to shapes that have the same form or pattern but are not necessarily the same size. Overlapping objects might be partially or fully on top of one another but do not imply that they are identical or congruent in size and shape. Expanded objects suggest a change in size rather than confirming that two shapes are the same; they may indicate growth or enlargement rather than a direct relationship of equality in dimensions. Thus, congruence is specifically the quality that relates directly to the ability to overlap precisely along a crease when folded.