Bridges are made of metal and concrete. They are outside and they heat up and cool down all the time. How might this factor into the design of a bridge? (We are learning about the molecules in solids, liquids and gases)

Which of these describes how heat is transferred by convection* a. sunlight travels through space without the aid of fluids or solids. b. warm air rises and takes the heat with it, eventually, it cools and sinks c. air at the equator rises and sinks at the poles. d. air molecules touch the warm ground, heating them up *not conduction