Answer:
Side AB
Step-by-step explanation:
Draw two congruent quadrilaterals.
Label the sides of one A,B,C,and D.
Label the sides of the other E,F,G,and H
Because the sides match up with the order in which they appear in if they are congruent, The first two letters(E and F) should be equivalent to the first two letters of the other shape(A and B).
