Final answer:
The Great Wall of China badge represents the concept of distance measurement. The badge symbolizes Casey's achievement of walking the same distance as this iconic landmark.
Step-by-step explanation:
The Great Wall of China badge that Casey earned on her Fitbit represents the concept of distance measurement.
The distance Casey accumulated, over 13,000 miles, is a representation of the distance the Great Wall of China spans. The badge symbolizes Casey's achievement of walking the same distance as this iconic landmark.