To show that \( \triangle ABC \cong \triangle XYZ \) by the Hypotenuse-Leg (HL) Congruence Theorem, we need to confirm that the legs of the triangles are congruent, given that the hypotenuses are already found to be congruent. Since angle B is congruent to angle Y and both triangles have congruent hypotenuses AC and XZ, we can conclude that it suffices to show that one corresponding leg is congruent.
Since we are looking for a corresponding part that must be congruent under the HL theorem, the correct response would be:
\( AB \cong XY \)
Thus, to satisfy the criteria for HL, you could select:
\( AB \cong XY \)
Therefore, the correct option is:
\( AB \cong XY \).