Answer:
c. Joints allow the roadway to expand and contract as cars put force on the bridge
Explanation:
The reasons why joints are allowed on roadway is to accommodate the contraction and expansion of the road as cars put force on them. 
- Most materials used in making roadways are susceptible to expansion and contraction. 
- When a measure of force is applied their length either increases or decreases depending on the type of force. 
- To accommodate these changes, joints are placed in roadways