Which statement explains why bridges may ice up before roads?

Answer: B — Cold air circulates above and below the bridge

The main idea is that bridges lose heat faster than roads because they are exposed to cold air on both sides. A bridge deck sits above open ground, so cold air can circulate over the top and flow beneath the structure as well. This convection pulls heat away from the surface from both directions, so the bridge cools more quickly and can reach freezing while nearby road surfaces, which are partly insulated by soil and can retain some heat, stay just above freezing. Additionally, bridges don’t have the earth to store warmth like roads do, and they shed heat to the night sky, speeding up radiational cooling. All of this means moisture on the bridge freezes earlier, causing ice to form before roads.