The Golden Gate Bridge is a steel structure 1,300 m in length. In order to compensate for changing temperatures, the bridge is designed with expansion joints that allow the structure to expand or contract. What is the purpose of these expansion joints?
1) To prevent the bridge from collapsing
2) To allow for the movement of the bridge due to temperature changes
3) To provide a place for pedestrians to walk across the bridge
4) To increase the strength of the bridge