Answer:
Dilation and reflection
Explanation:
The operations:
Rotation
Reflection
Translation
do NOT change the actual dimensions of the triangle's sides, the side lengths remain the same, so the triangles remain congruent.
On the other hand, if one includes Dilation in the transformations, the triangle's sides get augmented in side (although proportional), therefore, the new triangle is not congruent with the original one, although due to proportionality of the dilation process, it remains "similar" to the original one.
Bottom line: the transformation listed as "Dilation and reflection" is the one that creates a similar but not congruent triangle.