To determine if segment \( NO \) is a copy of segment \( PQ \), Thuy needs to measure the length of one of the segments and see if the corresponding segment is the same length from the same starting point.
The correct response is:
She must measure the distance from point \( M \) to point \( Q \) using a compass and place the compass on point \( M \) to see if point \( O \) is the same distance.
This option ensures that the distance from point \( M \) to point \( Q \) is replicated from point \( M \) to point \( O \), verifying that segment \( NO \) is a constructed copy of segment \( PQ \).