Final answer:
Steel should be avoided in bridges because of its expansion and contraction with temperature changes, susceptibility to corrosion, and tendency to bend under heavy loads.
Step-by-step explanation:
One of the reasons to avoid using steel in a bridge is because it expands and contracts with changes in temperature. This thermal expansion can cause stress and structural damage to the bridge over time. Another reason is that steel is prone to corrosion, especially when exposed to moisture and salt spray, which can compromise the integrity of the bridge. Lastly, steel is not the best material for bridges that experience heavy loads, as it can bend under high levels of stress.