Bridges freeze before roads because

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

Bridges freeze first because they lose heat to cold air on both sides. The bridge deck is exposed above and below, so convection pulls heat away from the surface from all around, causing it to chill and ice to form more quickly. Roads sit on the ground, which retains heat from the earth and sun, so they stay warmer longer and ice forms later. The other ideas don’t fit as well: sunlight alone isn’t the deciding factor, anti-freeze treatment isn’t a normal factor for road surfaces, and traffic doesn’t reliably prevent ice.