To determine which angle ∠A" is congruent to, I would typically need to see the diagram you mentioned showing triangles D E F and A" B" C".
However, if you know how the triangles are labeled, you can usually deduce the angle congruence based on the AAS (Angle-Angle-Side) Congruence Theorem. This theorem states that if two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent.
If you have the corresponding angles identified between triangles D E F and A" B" C", you can identify which angle ∠A" corresponds to from the options listed.
If you provide more specific information about the diagram or the angles, I can assist you further in identifying the correct option.