Geometry

Question Analysis: This question involves recognizing transformations that preserve congruency.

Key Concept Explanation:
A transformation preserves congruency if it does not change the size or shape of a polygon.
Such transformations include translations, rotations, and reflections.

Step-by-Step Solution:
Dilation and enlargement change the size, so they do not guarantee congruency.
Stretching distorts the shape, making it non-congruent.
Reflection preserves both size and shape, making the image congruent to the original.

Option Analysis:
(A) Incorrect: Dilation changes size (except...