Final answer:
In similar trapezoids, corresponding sides are proportional. The side AD of trapezoid ABCD is proportional to side EH of trapezoid EFGH.
Step-by-step explanation:
The student has asked which side of trapezoid EFGH is proportional to side AD of trapezoid ABCD, assuming that the trapezoids are similar. In similar trapezoids, corresponding sides are proportional. Thus, since AD is a non-parallel side in trapezoid ABCD, the corresponding non-parallel side in trapezoid EFGH would also need to be identified.
In this case, the corresponding sides to AD would be EH in trapezoid EFGH. Side AD of trapezoid ABCD is proportional to side EH of trapezoid EFGH.