To complete the proof that consecutive interior angles are supplementary, we need to determine what justifies the statement that the measures of angles A and E are equal.
Given the context, we can see that angles A and E are corresponding angles formed when two parallel lines (n and m) are crossed by a transversal. According to the Corresponding Angles Postulate, when two parallel lines are intersected by a transversal, the corresponding angles are equal.
Thus, the correct response to complete the proof is:
Corresponding Angles Postulate