Based only on the information given in the diagram, which congruence theorems or postulates could be given as reasons why DEF KLM?

I saw the diagram. 2 right triangles. Long legs have equal measure and short legs have equal measure.

This is a SAS congruence theory.

SAS stands for Side, Angle, Side. Two triangles are congruent because both have 2 sides of equal measure as well as an angle.