Answer: The answers is alternate interior angles.
Step-by-step explanation: First of all, the questions marks given in the figure are renamed in the attached figure as (a), (b), (c) and (d).
For (a): Since AC is parallel to A'C' and A'D is a transversal for these two parallel lines, so, ∠CDB' = ∠B'A'C', because these are alternate interior angles.
For (b): Since BC is parallel to B'C' and A'B' is a transversal, so ∠BEB' = ∠A'B'C', because these are alternate interior angles.
For (c): Since AB is parallel to A'B' and AD is a transversal, so ∠BAC = ∠CDB', because these are alternate interior angles.
For (d): Since AB is parallel to A'B' and BE is a transversal, so ∠ABC = ∠BEB', because these are alternate interior angles.
Thus, all the questions marks are the reasons that the given angles are equal because they are alternate interior angles.